This work used acoustic emission (AE) technique to detect machining vibrations during robotic milling process, and elaborated the impact mechanism of milling vibrations on surface roughness and residual stress. The findings indicated that the features relating to machining vibration included a sudden increase of amplitude in the time domain, and variations of frequency distribution in the frequency domain. The duration of machining vibration was exceedingly brief, and the changes of frequency distribution were mainly concentrated in 150–730 kHz. For the processing of AE signals, wavelet energy entroy (WEE) was selected as a detection indicator to monitor machining vibration. A laser vibrometer was also used to collect radial vibration signals for verification, which have similar characteristics with AE signals, confirming the effectiveness of vibration detecting based on AE method. At low spindle speeds, machining vibration is prone to occur at the cut-in and cut-out positions, and tends to become more frequent with the increase of feed speed. High spindle speed and low feed speed can effectively avoid the occurrence of machining vibration. The severe machining vibration occurred when the milling speed was set at 10,000 rpm with feed speed of 1440 mm/min. The influence of robotic milling vibration on surface integrity was also evaluated in details. The amplitude and frequency of machining vibrations during the robotic milling process are random, making the impact mechanism on surface integrity highly complex. Depending on specific conditions, these vibrations could result in deteriorated milling surfaces.
The field of abrasion has a long history and continues to be highly regarded despite being an older technology. It has consistently evolved, particularly with a growing focus on high-precision sectors such as aerospace and semiconductors. However, these advancements are accompanied by increasing environmental and health concerns related to abrasion processes, highlighting the imperative to minimize energy and material consumption. Due to the issues with traditional abrasion and the demand for precision abrasion, robotic abrasion has been proposed. This research categorizes abrasion robots based on their operational mechanisms and the characteristics of the target surfaces they are designed to treat. Additionally, it analyzes force control and path-planning techniques essential for achieving uniform abrasion and high-quality surface finishes. Moreover, recent literature on enhanced control and automation, including studies incorporating artificial intelligence, is also reviewed. Through a detailed examination, this study proposes a framework for standardizing the evaluation metrics in abrasion robotics, aiming to address the current lack of consistent criteria and facilitate further research and development.
The increasing demand for versatile graphene-based materials, incorporating semimetal nanoparticles (NPs), is driving contemporary societies towards platforms that harness solar radiation for biocidal activity, de-icing, and photodegradation. This study investigates the photoinduced antibacterial activity, de-icing, and photocatalytic properties of Cu-doped TiO2/Ultraviolet (UV)-Laser-Induced Graphene (LIG). Cu-doped TiO2/UV-LIG exhibits considerable promise when subjected to solar radiation, particularly in applications such as de-icing, photodegradation and antibacterial efficacy. Characterized by nanopores and a surface area of 396 m2/g, Cu-doped TiO2/UV-LIG achieved a noteworthy temperature of 91.7°C under 1 SUN irradiance, thus establishing a significant milestone in the field of LIG. Initially, it demonstrated exceptional phenol degradation efficiency at 86%, and this efficiency remained noteworthy at 83% even after undergoing five cycles of use, thus emphasizing its enduring degradation capacity. Moreover, at 0.5 SUN intensity, it demonstrated remarkable efficacy in eradicating over 99.999% of foodborne pathogens.
TiC-reinforced composite coatings were fabricated in situ on carbon steel plates using flux-cored arc welding with tubular wire. The flux was composed of titanium powder recycled from chips generated during the machining process. The microstructure of the welded deposits was formed using various metal strip thicknesses to fabricate the wires, resulting in different flux fill values. During welding, titanium chips melted and reacted with carbon to form TiC. The complex in situ-formed phases were beneficial for improving the coating properties. Results indicated that the microhardness of the composite coatings using a greater quantity of flux was enhanced to over four times that of the substrate. More TiC resulted in better hardness values with increased amounts of flux. However, using thick metal strips reduces the flux supply, thereby diminishing the formation of a wear-resistant microstructure.
With the growing awareness of mitigating greenhouse gas emissions, developing bio-based, multi-functional, water-based and high-performance resins is in urgent demand for structural applications. This study demonstrates how water-based lignin-polyvinyl alcohol (PVA) resins can be used as a matrix in natural-fiber-reinforced composites for high-performance applications. The lignin-derived water-based resin is synthesized by blending demethylated lignin quinone (DLq) and PVA to obtain PVA-blended-DLq (PDLq) resin, followed by thermal curing. Compared to neat PVA, the optimized PDLq resin demonstrates a significant 30.5% increase in tensile strength to 162.86 MPa and a 45% improvement in Young’s modulus to 8.52 GPa. It also shows good UV shielding performance, around 100% for UVB and 99.5% for UVA. Compared to previously reported jute composites, the treated jute fiber (TJF)-reinforced PDLq composite fabricated through hot pressing demonstrates superior flexural strength, 190.9 ± 7.1 MPa and flexural modulus, ~ 13.8 GPa. The water-based PDLq resin synthesized shows potential for UV shielding and all-green natural-fiber-reinforced PDLq composite for indoor high-performance applications.
Structural batteries are multi-functional composites that combine the functions of energy storage and mechanical load support. Bipolar current collectors allow batteries to be electrically stacked in series, increasing power and energy density while maintaining device integrity. In this study, bipolar current collectors (CCs) were fabricated in a sheet of carbon fiber fabric impregnated with an epoxy resin using vacuum-assisted resin transfer molding. Pressure was applied during the resin curing process to improve the mechanical properties of the bipolar CCs. The CC produced at an optimum pressure of 6.0 bar showed excellent mechanical properties, with a tensile strength and modulus of 833 MPa and 63.6 GPa, respectively, and exhibited a low through-plane resistivity of 4.9 Ω cm, facilitating efficient electron transfer between the stacked batteries. The electrochemical stability of the CCs was excellent over a wide voltage window of 2.45 V, even under harsh acidic and alkaline electrolyte conditions. To demonstrate the scalability of the device in terms of power and energy density, zinc-ion based structural batteries were fabricated by alternately stacking the batteries using the CC. The implementation of the CC presented here could lead to a significant improvement in the performance by reducing the weight and volume of the device.
Enhancing the transverse velocity to the catalyst layer and exploiting the over-rib convection are popular methods for improving the power output of proton exchange membrane fuel cells (PEMFCs). The trap channel configuration for optimizing the cathode channel offers a simple and inexpensive solution for design and manufacture. This study investigated a three-channel PEMFC model with and without integrating trap channels. The simulation study revealed that the channel with trap configuration produces higher power than the original straight channel without causing an increase in pressure drop. The implementation of traps formed high transverse velocity zones at the end of each trap and increased the O2 molar concentration at the gas diffusion layer (GDL)|catalyst layer (CL) interface but reduced the velocity magnitudes at the bipolar plate (BP)|GDL interface. Conversely, the staggered trap configuration exhibited a substantial positive impact on PEMFC performance through the augmentation of over-rib convection. The staggered configuration significantly outperformed the in-line trap configuration, yielding a remarkable maximum performance increase of 5.23% compared with the 2.07% enhancement observed in the in-line case.
Aluminum 6082 alloys are commonly utilized in significant industries because of their unique characteristics. However, they exhibit poor machinability as a result of their high ductility, high thermal expansion coefficient, and tendency to built-up edge formation. Considering the alloy's widespread usage, the difficulty of machining it raises sustainability concerns. For this reason, although minimum quantity lubrication (MQL) methods using various nanoparticle-added nanofluids have been used to enhance machinability, the use of graphene nanoparticles (GNP) has been ignored. Furthermore, there has been a lack of sustainability assessment and optimization. In the presented study, MQL methods using various GNP-added nanofluid (N-MQL) was used for the first time in the milling of Al6082 alloy, and its machining responses (cutting temperature, cutting force, feed force, surface roughness, and chip morphology) and sustainability indicators (carbon emission and total machining cost) were determined and compared with dry-cutting and pure MQL utilizing vegetable cutting oil. The utilization of the N-MQL, as opposed to the dry-cutting with appropriate cutting parameters, resulted in improvements of 50.6% in cutting force, 65.4% in feed force, 50.6% in cutting temperature, 33.2% in chip width, 15.3% in chip length, 67.3% in surface roughness, 21.5% in carbon emissions, and 52.6% in machining cost. Finally, applying multi-objective optimization using NSGA-II (non-dominant sequencing genetic algorithm II) and the multi-criteria decision-making method using VIKOR, optimum process parameters were determined in terms of sustainability-weighed carbon emissions and total machining cost. From the sustainability-based optimization results, it was determined that the cutting speed should be selected between 36 and 40 m/min, the feed should be selected between 0.14 and 0.18 mm/rev, and the N-MQL method should be used. Using the N-MQL method at above-average cutting speeds and feed values are the most sustainable machining parameters and condition for milling of Al6082.
The application of the mechanochemical effect as a means to enhance the cutting performance of gummy metals represents a pioneering approach in machining. In this study, we introduce static electricity to improve the machinability of aluminum under the mechanochemical effect. This method involves applying n-propanol to the workpiece surface under the influence of static electricity before the machining. Various deformation behaviors of aluminum cutting layers during orthogonal cutting are analyzed using high-speed in situ imaging and digital image correlation. Furthermore, the synergistic effect of static electricity on mechanochemical effect is verified by combining cutting force and machined surface quality measurements. The results show that the use of n-propanol under static electricity results in reduced cutting deformation, decreased strain rate and a more uniform strain distribution in the primary shear zone compared to surfaces solely coated with n-propanol. Consequently, this reduced deformation mode induces chip thinning and lowers cutting force by about 60% and 10%, respectively. The workpiece surface exhibits improved smoothness, with material pull-outs and pits nearly disappearing. It is found that these phenomena can be attributed to electrostatic catalysis, where a large number of electrons catalyze the reaction between active alcohol molecules and aluminum, forming a richer alkoxide film that enhances the mechanochemical effect.
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