Roughness Formation Research Articles

Experimental study on laser cutting process of simulated fast Reactor fuel rods

The cladding of fast reactor fuel rods, made of stainless steel, presents significant challenges in cutting due to its ductility, which leads to increased tool wear and poor cut quality with traditional mechanical methods. Laser cutting has emerged as a superior alternative, offering non-contact precision, high efficiency, and suitability for radioactive environments. This study systematically investigates the effects of laser cutting parameters—cutting speed, focal position, power, and gas pressure—on the cutting quality of simulated fast reactor fuel rods. The results show that optimal cutting is achieved with a cutting speed of 1 m/min, a focal position between − 20 and − 25 mm, a laser power between 7200 and 9600 W, and a gas pressure of 10 MPa. These parameters provide the best balance between cutting efficiency, surface roughness, and minimal slag formation. This study contributes valuable insights into optimizing laser cutting technology for nuclear fuel rod processing, with potential applications in fuel reprocessing and decommissioning.

Biocompatibility and drug release kinetics of TiNbZrSn femtosecond laser-induced superhydrophilic structures

As load-bearing components, metallic implants are frequently used for orthopedic prostheses due to their superiority over conventional ceramic and polymeric biomaterials. Metal-based orthopedic implants have been subjected to various fabrication and treatment methods to enhance their biological activities at the host site. Modifying the structure, improving the hydrophilicity, and developing controlled-release drug delivery systems can improve cellular adhesion, proliferation, osseointegration, and differentiation. Ultrafast lasers have recently attracted interest in surface engineering. Laser surface structuring permits the alteration of sample topography, the chemical makeup of the surface, and the material physical properties. This study presents the surface modification of a TiNbZrSn shape memory alloy using a femtosecond laser to produce laser-induced periodic structures with better drug release than that of a pristine sample. We also present the in vitro cell viability and biocompatibility of the alloy system. All samples structured with femtosecond laser exhibited superhydrophilic nature with 0° contact angle. In addition, the laser structured surfaces showed cell viability above 80 % and minimal cytotoxicity towards human keratinocytes. Moreover, a well-defined hydroxyapatite layer developed on the laser structured surface. In general, the laser structuring process and the induced changes on the surface in terms of roughness and oxide formation result in slower drug release (up to 10 %) compared to pristine specimens.

Photoaging effects on polyethylene microplastics: Structural changes and chlorpyrifos adsorption

Microplastics (MP) are a global concern due to their small size, insolubility in water, and non-degradable nature, and long-term environmental persistence. Weathering processes, such as ultraviolet (UV) radiation, can alter their properties, enhancing their ability to absorb pollutants or release harmful substances, such as pesticides, which is also an environmental concern, thereby complicating their environmental impact and mitigation efforts. This study investigates the impact of UVB-induced photoaging on polyethylene (PE) microplastics and their sorption behavior towards the pesticide chlorpyrifos (CP). PE microplastics were exposed to varying UVB aging durations, leading to significant changes in their physicochemical and morphological properties. The sorption experiments revealed that aged microplastics exhibited increased affinity for CP, with adsorption capacity rising by 17.9% compared to pristine PE. This enhanced adsorption was attributed to the (1) introduction of oxygen-containing functional groups, facilitating the formation of hydrogen bonds between the microplastic surface and surrounding water molecules, thereby contributing to the adsorption of CP; (2) formation of irregular micropores and surface roughness, potentially providing ample sites for pesticide adsorption and (3) reduction in crystallinity from 35% to 30%, which favors the sorption of hydrophobic organic pollutants. Density Functional Theory (DFT) calculations supported these findings by showing changes in the electronic structure of PE that facilitate interactions with CP. These results provide critical insights into the environmental behavior of aged microplastics and their potential to adsorb hazardous chemicals, underscoring the need for further research on the environmental impact of microplastic aging.

The effect of soaking heat-polymerized acrylic resin denture base in avocado seed extract (Persea americana Mill.) on the inhibition of denture-plaque microorganisms biofilm growth

Background Heat polymerized acrylic (HPA) resins are known to have high porosity that contributes to increased surface roughness and microcrack formation in stress areas. This facilitates the attachment and growth of polymicrobial biofilms contributing to increased antimicrobial resistance. Many research had been carried out on avocado seeds, but no research that studies avocado seeds effect on denture-plaque microorganism biofilm on HPA resin has been found. Methods This study used 144 samples (n=144), namely HPA resin discs covered with mono-species and polymicrobial biofilms. The discs were soaked for 8 hours in the 5%, 10%, 15%, 20% avocado seed extract, positive control (alkaline peroxide), and negative control (aquadest). Each disc was shaken with a vortex mixer for 1 minute, and 100 μL was added into 96-well microplates with three times repetition and incubated for 24 hours. A microtiter plate biofilm formation assay was then conducted The inhibition values were determined from the percentage inhibition value formula which required absorption values from a microplate reader (595 nm). The research data were analyzed using a univariant test, and a one-way ANOVA test, accompanied by Welch ANOVA on non-homogenous data. Results In this research, it was found that the MBIC50 of avocado seed extract against the mono-species of C. albicans (5%), C. glabrata (5%), A. odontolyticus (15%), S. gordonii (15%), S. aureus (10%), while against polymicrobial was 20%. There was a significant effect of soaking HPA resin in avocado seed extract on the inhibition of mono-species and polymicrobial biofilms with a value of p<0.001 (p<0.05). Conclusion The MBIC50 of avocado seed extract in polymicrobial biofilm group was higher than that in the mono-species biofilm groups. Although alkaline peroxide showed higher inhibition value than that of the MBIC50 in polymicrobial biofilm group, 20% avocado seed extract was concluded effective as it inhibited >50% polymicrobial biofilm.

Comprehensive analysis of Hibisci mutabilis Folium extract's mechanisms in alleviating UV-induced skin photoaging through enhanced network pharmacology and experimental validation.

Skin photoaging induced by ultraviolet A (UVA) and ultraviolet B (UVB) radiation manifests as skin roughness, desquamation, pigmentation, and wrinkle formation. Current treatments, such as sunscreen, hormones, and antioxidants, have limitations and side effects. Traditional Chinese Medicine Hibisci Mutabilis Folium (HMF), or Mu-Fu-Rong-Ye in Chinese name, refers to the dried leaves of the plant Hibiscus mutabilis L., which belongs to the Malvaceae family. It has been used traditionally to treat acute mastitis, parotitis, neurodermatitis, burns. The reported activities of HMF include anti-inflammatory and anti-oxidant effects. However, the therapeutic potential of HMF in preventing and treating UV-induced skin photoaging remains unexplored. This study aimed to investigate the protective effects of HMF extract (EHMF) against UV-induced skin photoaging and the underlying mechanisms of action, by using network pharmacology and experimental verification. Network pharmacology was employed to identify the effective chemical components of EHMF. Potential targets were identified via PPI network analysis. Representative compounds were characterized using UPLC-MS/MS. In vitro validation involved assessing HaCaT cell viability, observing live/dead cell staining through fluorescence microscopy, and measuring inflammatory factors using ELISA. For in vivo validation, a UV-induced skin photoaging mice model was treated transdermally with EHMF or Methotrexate daily for 7 days. Dermatitis severity, skin morphology, and collagen fiber pathology were evaluated. Inflammatory cytokine and protein expression in dorsal skin lesions was confirmed using Elisa Kits, Western blot and immunohistochemistry. A total of 22 active ingredients of EHMF were identified. GO enrichment and KEGG pathway analyses revealed a focus on inflammatory signaling pathways. In vitro experiments showed that EHMF significantly reduced UV-induced inflammatory factors in HaCaT cells and improved cell survival rates. In vivo, EHMF alleviated back skin lesions in UV-exposed mice, reducing epidermal and dermal thickening and pathological inflammatory cell infiltration. It also decreased abnormal MMP-9 expression and collagen fiber proliferation, along with levels of inflammatory factors like TNF-α, IL-6, IL-17, and EGFR. Western blot and immunohistochemistry results indicated that the over-activation of the AKT-STAT3 signaling pathway was inhibited. EHMF effectively reduced UV-induced skin damage, inflammation, and wrinkles, providing strong support for its clinical application as a dermatological agent.

Experimental evaluation of different coated cutting tools effects on machinability in turning of 17-4 PH stainless steel and optimization of the cutting parameters

Generally, coated cutting tools are preferred in machining of stainless steel. Especially, CVD coated cutting tools come to the forefront owing to its multilayer structure in the industry. In this study, the effects of CVD and PVD coated cutting tools on machinability were investigated in dry turning of 17-4 PH stainless steel. The cutting tools have exactly the same tool geometry. Based on the Taguchi L16 experimental design, experiments were performed for each coating type at different cutting speeds, feed rates and cutting depths. The evaluation parameters were selected as cutting force, surface roughness, tool life and chip formation. The effect ratio of input parameters to output parameters was evaluated with ANOVA and optimum cutting parameters were determined for each coating type with regression analysis. As a result of this study, PVD coated cutting tools showed superior performance than CVD coated cutting tools. It can be said that PVD coated cutting tools are a great alternative to CVD coated cutting tools in machining of 17-4 PH stainless steel.

The impact of heat treatment process on the drilling characteristics of Al–5Si–1Cu–Mg alloy produced by sand casting

Aluminum–Silicon (Al–Si) based materials are commonly preferred in engineering studies requiring high mechanical performance as an alternative to steel materials. These alloys are especially preferred in the automotive industry, aerospace components and heavy machinery parts. In post-casting processes, machining operations are of great importance for high geometric precision, surface quality and longer fatigue life in mechanical environments. In this research, the microstructural, mechanical and machining characteristics of the Al–5Si–1Cu–Mg material produced by sand casting method in both as-cast (AC) and heat-treated (HTed) (Solid solution, quenching and aging-SQA) states were experimentally investigated. Microstructural examinations were carried out with optical microscope and SEM images. Mechanical properties were determined by tensile and hardness tests. Then, drilling experiments were performed in the CNC vertical machining center with 8 mm diameter uncoated HSS (High Speed Steel) cutting tools at constant cutting conditions (i.e., cutting speed-V: 125 m/min, feed rate-f: 0.05 mm/rev and depth of cut-DoC: 15 mm). In microstructural investigations, it was determined that the microstructure of the Al–5Si–1Cu–Mg material in AC state consists of α-Al, eutectic Si, β-Fe (β-Al5FeSi) and π-Fe (π-Al8Mg3FeSi6) intermetallics. After the SQA, the existing phases generally exhibited a spherical structure, and it was seen that the β phase in the microstructure transformed into the Ɵ (Al7FeCu2) phase. SQA improved the hardness, yield and tensile durability of the material, whereas decreasing the elongation to fracture. SQA process improved the machining characteristics of the material by decreasing thrust force, moment, surface roughness and built-up edge (BUE) formation. The machined subsurface structure of HTed alloy under constant cutting conditions was determined to be more stable and smooth and the machined surface microhardness of HTed alloy was higher compared to as-cast alloy due to the effect of solid precipitation hardening. In addition, shorter and more broken chips occurred in the machining of HTed alloys due to the effect of low elongation to fracture.

Change in Surface Roughness on the Inner and Outer Surfaces of the Microtube during Hollow Sinking.

Hollow sinking experiments and tensile tests were conducted to clarify the evolution of surface roughness during hollow sinking. Stainless steel tubes (outer diameter: 1.5 mm; wall thickness: 0.045 mm) featuring a single grain spanning the wall thickness achieved via annealing as the starting material. The tube was drawn without an internal tool using a draw bench by controlling the tube drawing speed ratio of the die entrance and exit sides. The surface roughnesses of the inner and outer surfaces at the die entrance and exit sides of the drawn tube were compared with the surface roughnesses of the inner and outer surfaces under the uniaxial tensile deformation of the starting material. As a result, two major findings were revealed; the surface roughness formation behavior during the hollow sinking; the uniaxial tensile deformation exhibits a tube on both sides of the entrance and the exit of a die. Former uniaxial tensile deformation forms surface roughness of the tube at the die-entrance-side. However, hollow sinking reduces the roughness. The tube keeps its small roughness even though it is applied the later uniaxial tensile deformation behind the die exit. Furthermore, the conventional formula to predict the surface roughness of a metal sheet caused by the uniaxial tensile deformation can predict the surface roughness of a tube in the hollow sinking. At both die entrance and exit sides, the roughness of the inner surface was larger than that of the outer surface at the die entrance and exit side. The outer surface of the tube contacts the inside of a die when the tube passes through the die. The height of the convex parts decreased at that moment. Hollow sinking suppressed the increase in surface roughness of the inner surface as the outer surface was smoothed in the die. However, due to the formation of surface roughness after leaving the die, there is an overall increasing trend in inner surface roughness.

Ultrasound-assisted vacuum drying of limequat peels and characterization of thermal, morphological and functional properties

This work aimed to determine drying behavior and energy consumption of limequat peels dried using ultrasound-assisted vacuum drying (UAVD), vacuum-assisted drying (VAD), oven drying (OD) and vacuum drying (VD), and investigate thermogravimetric decomposition, morphological, elemental and spectral analyses of dried peels with energy efficiency analysis including specific moisture extraction rate (SMER), moisture extraction rate (MER) and specific energy consumption (SEC). The UAVD considerably shortened drying time by 49 %, 34 % and 15 % as compared to the OD, VAD and VD. The highest drying rate was achieved at the UAVD. The effective moisture diffusivity(Deff) values in descending order were UAVD>VD>VAD>OD. Proximate analysis showed that limequat peels dried using the UAVD had the highest fixed carbon (25.35 %) and ash (3.03 %) contents, but the lowest volatile matter (61.68 %). Dried limequat peels exhibited similar thermal decomposition behavior. The UAVD caused porous and rough surface formation, and microchanneling effect. Carbon (>62.56 %) and oxygen (>15.98 %) were the major elements in dried limequat peels. The lowest O/C (0.25) and H/C (0.85) ratios were obtained for the limequat peels dried using the UAVD. Fourier-transform infrared spectroscopy (FTIR) spectra showed primarily O–H, C–H, CO, CC and C–O–C stretching vibrations. The highest SMER (0.0053 kg/kWh) and MER (0.0012 kg/h) values, and the lowest SEC (188.27 kWh/kg) value were determined for the UAVD. In conclusion, the UAVD was found to be the most appropriate drying method for the drying of limequat peels.

The effect of soaking heat-polymerized acrylic resin denture base in avocado seed extract (Persea americana Mill.) on the inhibition of denture-plaque microorganisms biofilm growth

Background Heat polymerized acrylic (HPA) resins are known to have high porosity that contributes to increased surface roughness and microcrack formation in stress areas. This facilitates the attachment and growth of polymicrobial biofilms contributing to increased antimicrobial resistance. Many research had been carried out on avocado seeds, but no research that studies the effect of avocado seeds on denture-plaque microorganism biofilm on HPA resin has been found. Methods This study used 144 samples (n=144), namely HPA resin discs covered with mono-species and polymicrobial biofilms consisting of Candida albicans, Candida glabrata, Actinomyces odontolyticus, Streptococcus gordonii, and Staphylococcus aureus. The discs were soaked for 8 hours in the 5%, 10%, 15%, 20% avocado seed extract, positive control (alkaline peroxide), and negative control (aquadest). Each disc was shaken with a vortex mixer for 1 minute, and 100 μL was added into 96-well microplates with three times repetition and incubated for 24 hours. The inhibition values were determined from the percentage inhibition value formula which required absorption values from a microplate reader (595 nm). Results In this research, it was found that the MBIC50 of avocado seed extract against the mono-species of C. albicans (5%), C. glabrata (5%), A. odontolyticus (15%), S. gordonii (15%), S. aureus (10%), while against the biofilm was 20%. There was a significant effect of soaking HPA resin in avocado seed extract of 5%, 10%, 15%, 20% on the inhibition of mono-species and polymicrobial biofilms of denture-plaque microorganisms with a value of p<0.001 (p<0.05). Conclusion The MBIC50 of avocado seed extract in polymicrobial biofilm group was higher than that in the mono-species biofilm groups. Although alkaline peroxide showed higher inhibition value than that of the MBIC50 in polymicrobial biofilm group, 20% avocado seed extract was effective in inhibiting polymicrobial biofilm because it was able to inhibit more than 50% polymicrobial biofilm.

Optimizing Milling Parameters for Enhanced Machinability of 3D-Printed Materials: An Analysis of PLA, PETG, and Carbon-Fiber-Reinforced PETG

Fused deposition modeling (FDM) is widely applied in various fields due to its affordability and ease of use. However, it faces challenges such as achieving high surface quality, precise dimensional tolerance, and overcoming anisotropic mechanical properties. This review analyzes and compares the machinability of 3D-printed PLA, PETG, and carbon-fiber-reinforced PETG, focusing on surface roughness and burr formation. A Design of Experiments (DoE) with a full-factorial design was used, considering three factors: rotation speed, feed rate, and depth of cut. Each factor had different levels: rotational speed at 3000, 5500, and 8000 rpm; feed rate at 400, 600, and 800 mm/min; and depth of cut at 0.2, 0.4, 0.6, and 0.8 mm. Machinability was evaluated by roughness and burr height using a profilometer for all the materials under the same milling conditions. To evaluate the statistical significance of the influence of various processing parameters on surface roughness and burr formation in 3D-printed components made of three different materials—PLA, PETG, and carbon-fiber-reinforced PETG—an analysis of variance (ANOVA) test was conducted. This analysis investigated whether variations in rotational speed, feed rate, and depth of cut resulted in measurable and significant differences in machinability results. Results showed that milling parameters significantly affect roughness and burr formation, with optimal conditions for minimizing any misalignment highlighting the trade-offs in parameter selection. These results provide insights into the post-processing of FDM-printed materials with milling, indicating the need for a balanced approach to parameter selection based on application-specific requirements.

Electrospun Composites of Chitosan with Cerium Oxide Nanoparticles for Wound Healing Applications: Characterization and Biocompatibility Evaluation In Vitro and In Vivo.

Cerium oxide nanoparticles (CeONPs), as part of tissue regeneration matrices, can protect cells from reactive oxygen species and oxidative stress. In addition, they can influence the properties of the scaffold, including its electrospinnability and mechanical strength. In this work, we prepared electrospun fiber mats from a chitosan and polyethylene oxide blend (CS-PEO) with the addition of ceria nanoparticles (CS-PEO-CeONP). The addition of CeONPs resulted in a smaller fiber diameter and higher swelling compared to CS-PEO fiber mats. CeONP-modified fiber mats also had a higher Young's modulus due to the reinforcing effect of the nanoparticles. Both mats had comparable adhesion and cytocompatibility to mesenchymal stem cells, which had a more rounded morphology on CS-PEO-CeONP compared to elongated cells on the CS-PEO mats. Biocompatibility in an in vivo rat model showed no acute toxicity, no septic or allergic inflammation, and no rough scar tissue formation. The degradation of both mats passed the stage of matrix swelling. CS-PEO-CeONP showed significantly slower biodegradation, with most of the matrix remaining in the tissue after 90 days. The reactive inflammation was aseptic in nature with the involvement of multinucleated foreign-body type giant cells and was significantly reduced by day 90. CeONPs induced the formation of the implant's connective tissue capsule. Thus, the introduction of CeONPs influenced the physicochemical properties and biological activity of CS-PEO nanofiber mats.

Biodegradable microplastics aging processes accelerated by returning straw in paddy soil

Biodegradable microplastics (MPs) have been released into agricultural soils and inevitably undergo various aging processes. Straw return is a popular agricultural management strategy in many countries. However, the effect of straw return on the aging process of biodegradable MPs in flooded paddy soil, which is crucial for studying the characteristics, fate, and environmental implications of biodegradable MPs, remains unclear. Here, we constructed a 180-day microcosm incubation to elucidate the aging mechanism of polylactic acid (PLA)-MPs in straw-enriched paddy soil. This study elucidated that the prominent aging characteristic of PLA-MPs occurred in the straw-enriched paddy soil, accompanied by increased chrominance (76.64–182.3 %), hydrophilicity (2.92–22.07 %), roughness (33.12–58.01 %), and biofilm formation (42.12–100.3 %) for the PLA-MPs, especially with 2 % (w/w) straw return treatment (P < 0.05). A 2 % straw return treatment has significantly impacted ester CO group changes in PLA-MPs, altered the MPs-attached soil bacterial communities composition, strengthened bacterial network structure, and increased soil proteinase K activity. The findings of this work demonstrated that flooded, straw-enriched paddy soil accelerated PLA-MPs aging affected by soil-water chemistry, soil microbe, and soil enzymatic. This study helps to deepen our understanding of the aging process of PLA-MPs in straw return paddy soil. Environmental implicationMicroplastics (MPs) are emerging contaminants in the global soil and terrestrial ecosystems. Biodegradable MPs are more likely to be formed and released into agricultural soils during aging. Straw return is a popular agricultural management strategy in many countries. Considering the wide use of plastic film, sewage sludge, plastic-coated fertilizer, and organic fertilizer in agricultural ecosystems, it is crucial to pay attention to the aging process of biodegradable MPs in straw-enriched paddy soil, which has not been adequately emphasized. This aspect has been overlooked in previous studies and threatens ecosystems. This study demonstrated that straw-enriched paddy soil accelerated polylactic acid (PLA)-MPs aging influenced by the dissolved organic matter, microorganisms, and enzyme activity associated with straw decomposition.

Analysis of Blackening Reaction of Zn–Mg–Al Alloy Coated Steel Prepared by Anodizing Process

The rising demand for black-treated steel faces challenges with conventional black painting due to issues like scratching and peeling, impacting corrosion resistance and aesthetics. This study explores an alternative method, anodic oxidation, to blacken the surfaces of galvanized or coated steel plates. Parameters like temperature, duration, current density, and gas type were varied during the blackening process. The investigation aimed to identify key factors influencing the blackening. Scanning electron microscopy observed the morphology, while energy-dispersive X-ray spectroscopy and glow discharge mass spectrometry analyzed the chemical composition distribution. X-ray diffraction and X-ray photoelectron spectroscopy conducted compound crystal structure analysis. Results indicate higher temperatures, longer durations, and higher current densities improve blackening through anodic oxidation. Increased magnesium proportion on the surface leads to roughness and porous magnesium oxide formation, enhancing light absorption and explaining the observed blackening effect.

Assessing sampling interval-dependent roughness in fractured steel fiber reinforced concrete using a double-exponential decay model

This study introduces a double-exponential decay (DED) model to investigate the sampling interval (δ)-dependent behavior of crack morphology roughness in steel fiber reinforced concrete (SFRC). The root mean square (Z2-3D) of the directional derivatives in 3D digital morphology is employed to quantify the roughness and its anisotropic behavior. Surface morphologies of 24 fractured specimens are captured by using a laser scanner and the obtained results are re-meshed based on the Point-Kriging algorithm. The roughness is represented by the ratio of surface area to projected area (RS) and Z2-3D values along different directions at various δs (4–3000 μm). The outcomes suggest that the values of RS and Z2-3D both decline, but the anisotropy of surface roughness is enhanced at an increased δ. The DED model is able to properly reflect the decay behavior in which the morphology roughness is classified into three corrugated components based on their distinct attenuation laws. A satisfactory agreement with the literature data is observed, validating the presented methodology. The reported findings in this work are useful for enhancing the understanding of the formation of crack morphology roughness and its relationship to the damage process of SFRC.

Machinability performance of different fiber orientations of roll wrapped CFRP pipes

AbstractIntegrating fiber reinforcement plastics (FRP) materials into the industry plays a key role especially for pipes. However, due to the production methods of CFRP pipes, surface finishing processes are inevitable at the end of production. Despite the widespread use of CFRP materials, the predominant focus in the literature has been on their mechanical performance. This study aims to contribute to the limited research on the machinability of CFRP materials. In this context, the turning machining process for CFRP pipes was experimentally investigated in the present study. For this purpose, carbon fiber pipes with an inner diameter of 30 mm and an outer diameter of 60 mm were produced and subjected to computer numerical control (CNC) turning. First, a cylindrical aluminum pipe is used as a mold to manufacture CFRP pipes. Unidirectional (UD) carbon fabrics were wrapped on these aluminum molds. Shrink tape was used to enhance the surface smoothness and required pressure to prevent delaminating of the end product during the process. UD carbon fabrics are wrapped on to the mold at the selected angles (0°, 45°, and 90°) and the CFRP pipe specimens were manufactured using epoxy matrix. Pipes were processed on CNC lathe at 120, 160, 200 rev/min speeds and f 0.4 mm/rev feed rate. The surfaces of the machined specimens were measured with a microscope and a surface roughness device. On the other hand, wear on the tools was observed after the process.Highlights CFRP pipes were produced with different fibre orientations, i.e., 0°, 45°, and 90°. All CFRP pipes are made under equal conditions and cured at 80°. Turning of CFRP pipes was examined under dry environments. Performance criteria: surface roughness, temperature, tool wear, and chip formation were explored. 45° fibre angles CFRP pipes showed the best machinability performance.

Biodegradation of polyurethanes by Staphylococcus warneri and by microbial co-culture

With the increasing production and use of polyurethanes (PUs), it is necessary to develop sustainable techniques for the remediation of plastic pollution. The use of microorganisms capable of biodegrading PUs may be an environmentally desirable solution for controlling these plastic contaminants. To contribute to the discovery of alternatives for the mitigation of plastics in the environment, this study aimed to explore the potential of StaphylococcuswarneriUFV_01.21, isolated from the gut of Galleria mellonellalarvae, for biodegradation of PU in pure culture and microbial co-culture with Serratia liquefaciensL135. S. warneri grew using Impranil® PU as the sole carbon source in pure culture and co-culture. With six days of incubation, the biodegradation of Impranil® in Luria Bertani broth was 96, 88 and 76%, while in minimal medium, it was 58, 54 and 42% for S. warneri, S. liquefaciens, and co-culture, respectively. In addition, S. warneri in pure culture or co-culture was able to biodegrade, adhere and form biofilms on the surfaces of Impranil® disks and poly[4,4′-methylenebis (phenyl isocyanate)-alt-1,4-butanediol/di(propylene glycol)/polycaprolactone] (PCLMDI) films. Scanning electron microscopy also revealed biodegradation by detecting the formation of cracks, furrows, pores, and roughness on the surfaces of inoculated PU, both with pure culture and microbial co-culture. This study is the first to demonstrate the potential of S. warneriin PU biodegradation.

Investigation of evolution of γ N phase and its effect on conductivity and corrosion resistance of plasma-nitrided 316 L stainless steel bipolar plate for proton exchange membrane fuel cell

In this work, the evolution of γ N phase and its effect on conductivity and corrosion resistance of plasma-nitrided 316 L stainless steel bipolar plate was investigated. The results shows that a certain thickness of uniform γ N phase layer was formed after plasma-nitriding treatment. As the increasing in plasma-nitriding time, the thickness of γ N phase layer and nitrogen atoms in γ N phase layer was increased gradually. As the plasma-nitriding time was larger than 10 h, a large amount of cracks was formed in γ N phase layer because the nitrogen atoms were diffused into γ phase to cause the serious lattice distortion. When the plasma-nitriding time was reached to 24 h, the Fe4N compound was found on the sample surface. After plasma-nitriding treatment, the conductivity and corrosion resistance of the sample was obviously enhanced compared with the untreated sample. With the increasing in the thickness of γ N phase layer, the interfacial contact resistance (ICR) and corrosion current of the sample was gradually reduced. The ICR of the sample was reduced to 7 mΩ under 10 h condition. However, the formation of Fe4N compound and high roughness contributed to the increase of ICR of the sample under 24 h condition, its value was reached to 15 mΩ. When the plasma-nitriding time was larger than 10 h, the corrosion resistance of the sample became poor. The formation of cracks in γ N phase layer and the high surface roughness resulted in the degradation of corrosion resistance of the sample. Under 5 h condition, the comprehensive properties of the sample were the best. The ICR and corrosion of the sample were current conductivity and corrosion resistance of the sample were 15 mΩ and 5.1 μA cm−2, which were low 4 times and 15 times compared with the untreated sample.

Surface Quality Related to Face Milling Parameters in 3D Printed Carbon Fiber-Reinforced PETG

Three-dimensional printing technology holds significant potential for enhancing the flexibility and cost-efficiency of producing carbon fiber-reinforced polymer composites (CFRPs). However, it faces limitations such as challenges in achieving high surface qualityand precise dimensional accuracy and managing the distinctive anisotropic mechanical properties that it demonstrates. This study aims to explore the machinability of 3D printed PETG infused with 20% short carbon fiber and to assess the resulting surface roughness and burr formation. Employing a Design of Experiments (DoE) approach, three factors were considered: rotational speed, feed rate, and depth of cut. These factors were tested at varying levels—rotational speeds of 3000, 5500, and 8000 rpm; feed rates of 400, 600, and 800 mm/min; and depth of cut values of 0.2, 0.4, 0.6, and 0.8 mm. The evaluation of machinability relied on two key response parameters: surface roughness (Sa) determined from the milled surface and burr height measured on both sides using a roughness meter. The findings revealed a significant influence of milling parameters on both roughness and burr formation. However, the ideal conditions for minimizing roughness and reducing burr formation did not align. Furthermore, a comparative analysis was conducted between these results and the machinability of PETG under similar conditions.

Influence of cutting tool design on ultrasonic-assisted drilling of fiber metal laminates

Ultrasonic-assisted drilling (UAD) is a machining process that is known to improve the hole quality and reduce cutting forces. Previous studies focused on optimizing cutting parameters to improve the hole quality in conventional drilling (CD) and UAD, as well as to finding the optimum vibration parameters (frequency and amplitude) that will increase the effectiveness of the UAD process. However, the influence of cutting tool type during UAD has been largely overlooked. This research aims to address this gap by analyzing the effect of cutting tool type during UAD on the cutting forces and hole quality in GLARE (Glass Laminate Aluminum-Reinforced Epoxy) laminates. Four types of drills, namely, twist drill (TD), double cone drill (DCD), a step drill type 1 (SD1), and step drill type 2 (SD2) with different step length, were selected for this study. The lowest thrust force (47.04 N) and torque (0.079 Nm) were achieved using twist drill, while DCD, SD1, and SD2 exhibited higher thrust forces (12.81%, 20.69%, 41.3%) and torques (94%, 92%, 91%), respectively. In addition, TD produced high-quality holes with lowest surface roughness (Ra 1.66 μm, Rz 10.58 μm) and minimal burr formation (entry burr height 152.3 μm, exit burr height 69.22 μm). Conversely, DCD, SD1, and SD2 showed higher surface roughness Ra (23%, 16%, 24%) and Rz (16%, 37%, 29%), respectively, compared to the TD. Holes drilled using SD1 and SD2 generally had smaller burr height. Overall, UAD system effectively reduced cutting forces at low spindle speed and feed rate. To achieve higher drilling quality, specifically to reduce the surface roughness and exit burr height, a medium spindle speed of 3000 rpm, a feed rate of 225 mm/min is recommended. Drilling at higher cutting parameters using UAD resulted in a decline in hole quality, except for entry burr height.