Primary Process Parameters Research Articles

Laser Hardening of Unimax Stainless Steel

Nowdays, laser hardening of materials brings a comparative advantage over the conventional hardening technique. Fast cooling rate due to the heat distribution through its own bulk material, self-quenching property (rapid cooling without external water or oil), environmentally friendly characteristics since the procedure does not exhaust smoke, the localized heat input due to adjustable laser spot size to avoid distortion and minimum time to finish the operation are some of the advantages to mention. NIKO is a company specialized in making electrical products like socket outlets and switches by using injection molding techniques. Unimax is a kind of stainless steel used by the company to prepare some parts of the injection molding components like a Nozzle. This time, the company is using more and more fiber-reinforced polymers throughout their product line. These composites are far stronger than the polymer, but on the downside, the fibers are quite abrasive. The objective of this research was to harden the Unimax stainless steel using Nd:YAG (neodymium-doped yttrium aluminum garnet) laser technique. First, the laser transverse speed and spot size were identified as the primary process parameters. Then, the traverse speed of 100, 150 and 400 mm/min and spot size of 2164, 2169, 2288 and 2412 um were assigned with 3 replications. Afterwards, thermal simulation was done using COMSOL Multiphysics© followed by the real test on the metal bar. Therefore, the highest hardness of 650 HV was obtained at a speed of 150 mm/min and a spot size of 2169 um diameters. Finally, the corresponding depth of hardness and roughness values of 200 um below the surface and unmelt samples respectively were obtained. HIGHLIGHTS Laser hardening of materials brings a comparative advantage over the conventional hardening technique The laser transverse speed and spot size were identified as the primary process parameters. Afterwards, thermal simulation was done using COMSOL Multiphysics© followed by the real test on the stainless steel bar The depth of hardening and Vickers hardness (HV) increased with the smaller spot size and slow traverse speed of the ND:YAG laser, but this resulted in a melt on the surface of the hardened metal One of the problems of making products using injection molding techniques using fiber-reinforced polymers is the abrasive nature of the fibers which widen the injection nozzle GRAPHICAL ABSTRACT

Ultrasonic pulsed waterjet surface peening of an industrial aluminum-based metal matrix composite

Peening is used across a wide range of materials to improve fatigue response. Recently, a new approach to peening has been developed using an ultrasonic-pulsed waterjet (UPWJ). In the present work, UPWJ peening has been conducted on a powder metallurgy derived aluminum-based metal matrix composite (Al-MMC), containing 5 wt% aluminum nitride (AlN) additions. Traverse speed is one of the most important parameters in UPWJ peening, which primarily modulates the mechanistic interaction between the waterjet and the target surface. In the current study, a focus was placed on assessing the effects of traverse speed (which was varied from 150 to 1000 mm/s), while the other primary process parameters, including the pressure, frequency and standoff distance were kept constant. Confocal laser scanning microscopy and scanning electron microscopy were used to evaluate the surface roughness and microstructure of the Al-MMC samples, in both un-peened and UPWJ peened states. The induced residual stress generated by UPWJ was also determined, with profiles obtained by electropolishing to remove micro-layers of material until an attenuation of the residual stresses was realized. It is shown that the Al-MMC was generally responsive to UPWJ peening. The surface roughness increased due to UPWJ processing, though the extent of increase was lower for increasing traverse speed. Mass losses were recorded at UPWJ traverse speeds lower than 500 mm/s due to material removal. Generally, the UPWJ peening process produced significant increases in compressive stresses, with the best combination of low surface roughness and high compressive stress obtained at a traverse speed of 700 mm/s.

Friction Stir Welding of Wrought Aluminium Alloy EN AW- 6082

The article presents results of the friction stir welding of 6 mm thick plates made of wrought aluminium alloy EN AW-6082. Tests discussed in the article involved the identification of the effect of primary welding process parameters on the quality of welds. Test welds were subjected to visual tests, measurements of temperature (inside the weld), tensile strength tests as well as macro and microscopic metallographic tests and structural tests (performed using a scanning electron microscope). The application of the appropriate values of the primary welding process parameters (i.e. the tool rotation rate and the welding rate) enabled the obtainment of the high and repeatable quality of FSW joints made of aluminium alloy EN AW-6082. The test results presented in the article can offer technological solutions for potential

Effect of welding speed on mechanical properties and corrosion resistance rates of filler induced friction stir welded AA6082 and AA5052 joints

Friction Stir Welding (FSW) was carried out to examine the influence of filler materials and varying process parameters on the microhardness and the joints corrosion resistance properties. Aluminium alloys 6082 and 5052, having 8 mm thickness was joined by varying parameters. The primary process parameters are rotational speed, tool travel speed, plunge depth, filler holes centre distance and filler ratio. The hardness at the weld nugget zone and corrosion rate evaluations were analyzed. The best results were obtained for the parameter combinations of 1150 rpm tool rotation, 130 mm min−1 tool travel, 0.2 mm tool plunge, the filler holes centre distance 2 mm and a powder filler made of 95% magnesium and 5% chromium.

Property prediction and crack growth behavior in cold sprayed Cu deposits

Low ductility of metallic deposits manufactured by cold spraying (CS) impedes potential mechanical performances in industrial applications. Through appropriate annealing treatment, the amount of both, non-bonded interfaces and work hardening promoted dislocations during CS can be significantly reduced. Consequently, the annealed samples exhibit higher strength and fracture strain than the as-deposited ones. Cu was selected as a reliable material for CS. To correlate Cu deposit strength with primary process parameters and material properties, the Cu powder strength was assessed. Crack characterization of Cu deposits was performed by in-situ microscopic observations during tensile testing. The direct observation of crack initiation, growth and final fracture allows revealing failure mechanisms. The in-situ tests allow distinguishing the effects of reduced initial defect sizes due to annealing and improved ductility in the vicinity of initial defects on possible crack growth and part failure. Considering the necessary compromise between strength, uniform elongation, ductility and microhardness, a post-spraying annealing process is desirable for CSed Cu deposits. The identification of macroscopic and micro-mechanical properties attained under respective process parameters and influences of annealing processes therefore allow identifying solutions for improvements of CSed deposits for load-carrying applications, which is a prerequisite for using CS as additive manufacturing technique.

An evolved native microalgal consortium-snow system for the bioremediation of biogas and centrate wastewater: Start-up, optimization and stabilization

It is necessary to develop sustainable technologies for centrate wastewater (CW) and biogas treatment from sludge anaerobic digestion (AD) systems in an environmentally friendly and economical manner. The microalgae-based bioremediation approach presents a competitive alternative due to its capacity for nutrient recovery and carbon sequestration. However, process instabilities and operating challenges limit its development and implementation largely due to the complexities in the CW and biogas. In this study, the evolved native microalgal consortium (ENMC) was firstly developed using the gradual stress increase method to enhance their adaptation in high ammonium condition. The supplementation of local snow (with Ca2+ and Mg2+) and biogas into CW significantly enhanced ENMC growth through batch tests. Subsequently, an integrated ENMC-snow (ENMCS) system was proposed consisting of a hydrolysis-acidification reactor (HAR), biogas upgrade reactor, and photobioreactor (PBR). The ENMCS system was systematically investigated under both batch and semi-continuous operations, by adjusting primary process parameters including the fill ratio, feeding time, hydraulic retention time (HRT), wastewater pretreatment, and PBR type. It was eventually optimized as a 24 h, 70% fermented CW diluted with 30% snow water, semi-continuous feeding system with a fill ratio of 50% and HRT of 6 d in an open-PBR. Long-term operation (310 days) showed superior biomass yield (0.3059 ± 0.0039 g/(L•d)) and nutrient removal efficiencies (95.6 ± 0.13% and 90.8 ± 0.44% for NH4+-N and PO43−-P removal). Meanwhile, biogas was upgraded with an 82.2% CO2 reduction. The economic and environmental analysis further demonstrated the ENMCS system as an effective alternative for the bioremediation of AD effluents while simultaneously producing value-added biomass, especially applicable to snowy regions.

P.081 Developmental progression of interneuron network deficits in a 15q13.3 microdeletion mouse model – a glimpse on adolescent priming for schizophrenia?

Roller compaction is a continuous dry granulation process, where the powder is compressed between two counter-rotating rollers and compacted into ribbons. The quality and homogeneity of the granulate is determined by the uniformity and porosity of the ribbon, which depends on the feeding process of the primary powder to the rollers, the flow properties of the primary powder and process parameters such as roller forces. Previous work was conducted to improve the powder flow and distribution in the feeding zone by developing new feeding guiders, which are located in the feeding zone close to the rollers on the lab-scale roller compactor Alexanderwerk WP120 Pharma (Yu et al., 2018). These new feeding guiders were used to reduce the amount of powder that is delivered to the centre of the rollers and increase the amount of powder that is delivered to the sides of the rollers, in comparison to the original feeding guiders. This modified concept using new feeding guiders has been applied to the large-scale roller compactor Alexanderwerk WP200 Pharma in the present work. In order to evaluate the homogeneity of the ribbon properties across the ribbon width, the temperature profile and porosity distribution across the ribbon width were measured. The new feeding guiders resulted in ribbons being produced with a more uniform temperature profile and porosity distribution across the ribbon width when using the small and large scale roller compactors at different process parameters.

Free Vibrational Characteristics of Dual Side Nd: YAG Laser Welded Stainless Steel 304 Joints Reinforced with Al <sub>2</sub> O <sub>3</sub> Micro Powder Particles

<div class="section abstract"><div class="htmlview paragraph">Nd: YAG Laser Welding Process (LWP) is the most efficient method commonly used for the joining of different kinds of materials, whether it can be a sheet or plate. LWP in general, uses high power density, frequency and travel speed or feed rate as primary process parameters in order to perform a joining process across the metals. This paper investigates the effect of free vibrational characteristics for Stainless Steel 304 (SS 304) joints which are reinforced with Al<sub>2</sub>O<sub>3</sub> micro particles processed by dual side (welding performed on the top and bottom surface of sheets) Nd: YAG LWP. The inclusion of micro particles was inserted directly across the weld pool region, by fabricating drills with a constant gap between each drilled holes. Totally 12 samples were fabricated with different laser power, travel speed and by keeping the frequency level as constant for all the experiments. Vibration tests were performed on the fabricated samples made with and without incorporation of micro particles using accelerometer, data acquisition card, and the plots were obtained with the assist of DEWE software. The vibration equipment is used on the SS 304 joints in order to process the vibrational signals. Each sample has been tested with ten trials and the average values are drawn in order to reduce or minimize the measuring errors like (measuring error, fitting error, environmental impacts, etc.). The results revealed that vibrational characteristics are linked to factors like reinforcement of powders, selection of welding process and process parameters. It is also understood that the frequency and damping factor for a material can be varied with process parameters and inclusion of micro particles in the solidification process. Thus this paper will assist any designer to choose the process parameter ranges, reinforcement of powder particle methodology and their impact on the material behavior of fabricated joints.</div></div>

Estimation of clad geometry and corresponding residual stress distribution in laser melting deposition: analytical modeling and experimental correlations

Laser melting deposition (LMD) is a promising technology to produce net-shape parts. The deposited layers' characteristics and induced residual stress distribution influence the quality, mechanical, and physical properties of the manufactured parts. In this study, two theoretical models are presented. Initially, the clad geometry of the 1st deposited layer is estimated using the primary process parameters. Then, a hatch distance is used to calculate the re-melting depth and total clad geometry for all the deposited layers. The output of the 1st model is then used as an input in the 2nd model to estimate the residual stress distribution within the substrate and deposited layers. The model, for clad geometry, is validated using published experimental data for the depositions of AISI316L powder debits on AISI321 bulk substrate by the LMD process. For the residual stress distribution model validation, the published experimental results for X-ray diffractometry, in case of AISI4340 steel powder debits depositions on the AISI4140 bulk substrate by the LMD setup, are used. It was found that the current models can estimate the clad geometry and induced residual stress distribution with an accuracy of 10–15 % mean absolute deviation. An optimum selection of hatch distance is necessary for proper energy density utilization and dimensional control stability. The induced residual stress distribution was caused by the heating and cooling mechanisms, which appeared due to rapid heating and moderate cooling, in combination with slow conduction. These phenomena became incrementally iterative with the number of layers to be deposited, thus presenting a direct relationship between the residual stress distribution and the number of layers deposited on the substrate. The proposed models have high computational efficiency without restoring the meshing and iterative calculations. The high prediction accuracy and computational efficiency allow the presented model to investigate further the part distortion, part porosity, life-expectancy and mechanical properties of the part, and process parameter planning.

Control of Porosity in Freeze Casting

Many biologic structural materials have porous microstructures with a distribution and orientation of pores that are challenging to achieve using traditional methods of processing. In this investigation, numerical and experimental methods of evaluation were used to understand effects from the primary processing parameters on the temperature gradients during solidification in freeze casting of ceramics. The location and orientation of the temperature gradients were found to be highly dependent on the geometrical and thermal properties of the mold material used in processing. Furthermore, it was found that careful control of these processing variables can be used to design bioinspired porous materials with graded orientations and distributions of pores.

Additive Manufacturing of Salt Hydrates: Primary Process Parameters and Case Study

This paper presents the latest outcomes in the field of additive manufacturing. Some salt hydrates as printing materials provide many advantages (such as good availability and low toxic behaviour) compared to other materials, thus making them particularly suitable for specific applications. A layered deposition method for salt hydrates is developed from the binary phase diagram of sodium acetate trihydrate, which is first described mathematically. The experimental results then verify the theoretically described method. Thus, the presented process can also be applied to other salt hydrates which are based on the same physical basic principles. Moreover, this novel process has been termed as Subcooled Liquid Printing (SLP) by the authors.

Application of feeding guiders to improve the powder distribution in the two scales of roller compactors.

Roller compaction is a continuous dry granulation process, where the powder is compressed between two counter-rotating rollers and compacted into ribbons. The quality and homogeneity of the granulate is determined by the uniformity and porosity of the ribbon, which depends on the feeding process of the primary powder to the rollers, the flow properties of the primary powder and process parameters such as roller forces. Previous work was conducted to improve the powder flow and distribution in the feeding zone by developing new feeding guiders, which are located in the feeding zone close to the rollers on the lab-scale roller compactor Alexanderwerk WP120 Pharma (Yu et al., 2018). These new feeding guiders were used to reduce the amount of powder that is delivered to the centre of the rollers and increase the amount of powder that is delivered to the sides of the rollers, in comparison to the original feeding guiders. This modified concept using new feeding guiders has been applied to the large-scale roller compactor Alexanderwerk WP200 Pharma in the present work. In order to evaluate the homogeneity of the ribbon properties across the ribbon width, the temperature profile and porosity distribution across the ribbon width were measured. The new feeding guiders resulted in ribbons being produced with a more uniform temperature profile and porosity distribution across the ribbon width when using the small and large scale roller compactors at different process parameters.

On the reliability of investment risk assessments

The paper examines the reliability of investment risk estimates based on probabilistic realizations of purpose-designed scenarios. The calculations of the probabilities of scenario realization were based on logical and probabilistic methods. The reliability of risk assessment is understood as the probability of successful completion of a project, fulfillment of all contractual obligations: construction in compliance with the architectural and engineering design and quality requirements, within the contractual period and approved budget. Investment risks were estimated based on eight primary scenarios. The realization of the risks of the main group depended on the realization of the various numbers of risk scenarios of each subgroups in the main group. For instance, the first scenario of the main group consisted in the risk of faulty project ROI analysis and the risk of underestimated construction budget. The second one consisted in the risk of underestimated construction budget and risk associated with the selection of the basic flowsheet and primary process parameters, etc. The risks of each subgroup could be obtained by means of expert estimations or, in case of sufficient statistical data, based on the actual distributions. A mathematical model was developed for the purpose of a computerized solution. The mathematical model also allowed identifying such dependability factors as “weight”, “significance” and “contribution” of each risk in the success of an investment project (reliability structure of investment risk estimation). The analysis of calculation data enabled the identification of the probability of successful project completion (reliability), the risks that are the most important, significant and having the largest contribution to the successful implementation of investment projects. Also, the risks were identified that have the least pronounced effect on the successful implementation of an investment project.

Primary Processing Parameters, Porosity Production, and Fatigue Prediction for Additively Manufactured Alloy 718

Powder bed fusion processes commonly introduce voids and defects into components. It has been shown that many of these features and their size and shape characteristics are controllable through process parameter manipulation, but this process is typically time-consuming and expensive. In spite of this, an experiment was developed to explore a wide region of laser powder bed fusion process space, and several void measurements were obtained to characterize component density percentage, pore size, and pore shape. Then, multiple models commonly used in the literature to predict porosity were examined and compared with the experimental data. Using the developed porosity model, a fatigue life prediction framework was adapted, and the predictions were compared to the previously published experimental data. Results of this investigation reveal the strengths and weaknesses of multiple literature models in predicting porosity, and they depict how porosity and resulting fatigue lives vary across process space.

Conversion of actinide nitrate surrogates into oxide using combustion synthesis process: A facile approach

In recent years, the focus of research in the conversion routes for the actinide nitrates into oxides for the generation IV nuclear fuel cycle have attracted rapidly growing interest. One process is the self-sustained exothermic reaction of Solution Combustion Synthesis (SCS) methodology. It was applied here to the reaction of an actinide surrogate Gd(NO3)3,6H2O with glycine in air to produce ∼10−3 mol amounts of Gd2O3. The primary process parameters were the Gd/glycine ratio and heating rate, which affected the ignition temperature of the precursor mixture. An optimum ratio of one and a heating rate of 10 K min−1 resulted in nearly complete SCS conversion over the 483–573 K temperature range and ultrafine gadolinia powders. The 100- to 500-fold swelling of the reactant mixture plays a dynamic role in the reactivity of the system. Final products were characterized by X-Rays Diffraction (XRD), surface area analysis, carbon content, and Scanning Electron Microscopy (SEM). The structural characteristics of the final gadolinia phases have been interpreted by the adiabatic flame temperature calculation.

The effect of primary processing parameters on surface roughness in laser powder bed additive manufacturing

Metal additive manufacturing (AM) is a method to create complex components in a layer-by-layer process. Laser powder bed fusion (LPBF) provides the ability to fabricate complex designs. Components with internal geometries have surfaces that are difficult to improve through post-processing and have been shown to be detrimental to mechanical performance. This work investigates the relationship between primary processing parameters, and surface roughness of nickel-based superalloy 718 fabricated on a LPBF AM machine. The surface roughness of components built using varied contour processing parameters was characterized using both nondestructive and destructive measurement techniques. Statistical correlations are presented between contour processing parameters and surface roughness height metrics along with general trends in the relationships. Results show that the destructive measurements are required to expose notch-like features that are obstructed by powder particles attached to the surface. However, nondestructive methods more easily provide a statistically significant sample size. Understanding the surface roughness can be used for further process optimization and to inform the qualification strategy for AM components.

Development of automated spray pyrolysis setup for chemical vapour deposition like growth of thin solid films

This paper presents a simple electronic interface for spray pyrolysis to deposit high quality thin solid films. The exhibited electronic circuit with the Arduino based microcontroller is acting as the interface between the primary process parameters and the computer running National Instruments{®} LabVIEW{®}. The proposed setup and deposition flow achieve a reproducible, repeatable, and uniform deposition of thin films through the spray pyrolysis technique, which improves the conventional spray pyrolysis technique. The conventional spray nozzle was replaced by the therapeutic aerosol nebulizer, a cost viable replacement, for uniform, smooth, chemical vapor deposition (CVD)-like deposition. The efficacy of the automated nebulizer spray pyrolysis (n-SP) setup was demonstrated by depositing fluorine doped tin oxide (SnO2:F), zinc oxide (ZnO) and zinc sulfide (ZnS) thin films and also by comparing the characterization results of the films with the literature. Results suggest that the proposed automated nebulizer spray pyrolysis setup has the ability to change the commercial production of device quality thin films from complex chemical vapor deposition to cost-effective, simple and automated nebulizer spray pyrolysis method.

Continuous DLP ceramic 3D printing

In order to resolve the problems of the low efficiency and the anisotropy of printed object in the traditional ceramic 3D printing techniques, a novel continuous digital light processing (DLP) ceramic 3D printing implemented by utilizing the combination of an oxygen-rich composite thin film and the resin-based ceramics slurry has been proposed and developed. The basic principle and the process flow of the proposed continuous ceramic 3D printing are described. Then, the ceramic slurry used for this proposed 3D printing technique is investigated and optimized, and the effects and the rules of primary process parameters on forming process are revealed by conducting a series of experiments. Finally, two typical cases are provided to demonstrate the feasibility and validity of the proposed process. As a result, a continuous DLP ceramic 3D printing has been fulfilled, which provides a promising and novel solution for high-efficiency, low-cost ceramic 3D printing.

Simulation of the multi-component process gas flow for the explanation of oxidation during laser cladding

Usually the process gas flow rates and the process gas types are not regarded as the primary process parameters of the laser cladding process. Herein it is shown, how the melt pool surface oxidation can be significantly reduced by the change of the carrier gas type, by a reduced carrier gas flow rate and by minor changes in the powder nozzle design. However, the absorptivity may decrease concurrently by up to 15%. A simulation model for the gas flow and the powder particle flow between the powder nozzle and the melt pool surface has been developed, which reveals the volume percentage of different gas types and so the quality of the shield gas atmosphere. Additionally, the powder particle distribution and the attenuation of the laser beam by the powder particles can be simulated. The simulation results are confirmed by experimental measurements of the powder particle density distribution in the working plane, by measurements of the oxygen volume percentage at the workpiece surface, by high-speed camera images of the melt pool surface and by absorptivity measurements, which show the effect of oxidation on the process.

Fabrication of polycaprolactone electrospun fibers with different hierarchical structures mimicking collagen fibrils for tissue engineering scaffolds

The ability to topographically mimic the surface features of collagen fibrils is an important step in the preparation of tissue engineering scaffolds. It is important to know which kinds of surface topographies of electrospun fibers are more favorable for cell growth. In this study, fibers with three kinds of hierarchical-structured surfaces were fabricated by electrospinning to mimic collagen fibrils. By combining thermally induced phase separation (TIPS) and non-solvent induced phase separation (NIPS), polycaprolactone (PCL) fibers with a porous surface were electrospun from PCL in a chloroform (CF)/dimethyl sulfoxide (DMSO) mixed solution. In addition, two additional types of fibrous membranes, with PCL fibers being the shish and decorated by PCL kebabs on the surface, were created by two different controlled homoepitaxic crystallization methods—the solution incubation method and the solvent evaporation method. It was found that the solvent evaporation method was more effective in forming kebabs and the primary optimal processing parameters were identified. The presence of pores on the fiber surfaces contributed to a much larger surface area and a higher total volume of pores. To investigate the cellular response on such scaffolds, 3T3 fibroblast cell and human umbilical vein endothelial cell (HUVEC) assays were conducted and the results indicated that both of the nanotopographies on the surfaces of the scaffolds improved cell viability and proliferation. Furthermore, the porous surface was more beneficial for enhancing cellular responses, which suggests better biocompatibility and greater potential to mimic collagen fibrils for tissue engineering application, and especially as scaffolds for endothelial layers in blood vessels.