Journal of Manufacturing Processes最新文献

This work is to investigate the subsurface damage distribution law and suppression methods in sapphire ultra-precision grinding. The grinding strategies of rough grinding, semi-finish grinding and ultra-precision grinding are used to suppress the subsurface damage, the effects of grinding wheel grit size and number of grinding passes on the subsurface damage are investigated. First, cross-section polishing, FIB, and ion beam polishing were employed to reveal the scale and distribution of subsurface damage. Second, chemical etching was performed on the subsurface, the subsurface cracks with different grinding strategies were exposed, and the crack distribution density was obtained by image processing. Then, the subsurface deformation behavior and microcrack formation mechanism were investigated by TEM. The damage scales of different grinding strategies were evaluated using photothermal absorption. Ultimate, ultra-precision grinding can control the subsurface damage scale to 3.9 μm, the mechanisms of subsurface damage generation and removal were revealed. Meanwhile, a subsurface damage model more suitable for the combined grinding strategy was proposed.

Flute grinding is a crucial process in solid end-mill manufacturing, because the generated flute parameters, i.e. helix angle, rake angle, core radius, and flute width, have significant effects on the cutting performance of end-mills. However, the flute grinding of non-cylindrical solid end-mills is still challenging due to the variation of the flute parameters along the tool axis. This paper proposes an accurate and efficient method of wheel path planning for flute grinding of non-cylindrical solid end-mills based on circular arc projection. The wheel path determined by the new method can accurately generate the designed helix angle, rake angle, core radius, and flute width, even if all of these parameters vary along the tool axis. The helix angle and rake angle are ensured by the conjugate condition between the wheel surface and the cutting-edge curve. Based on circular arc projection, equivalent errors of the core radius and flute width are introduced to quantify the machining errors of the two parameters, without the need to predict the flute profile. Simulations and experiments are conducted to validate the proposed method. Three types of non-cylindrical end-mills i.e. tapered end-mill, tapered barrel end-mill, and barrel end-mill, are considered in the validation. The measured results indicate that the generated flute parameters coincide well with the designed ones at different axial positions of the end-mills.

To reduce the prediction error of traditional Sims rolling force model (abbreviated as the Sims model), a new prediction model of hot rolling force is established by modifying the Sims model with the adaptive exponential smoothing method using industrial-measured data. Firstly, statistical analysis of industrial-measured rolling force is carried out, and the discrete distribution characteristic of the data is revealed. Then, an adaptive correction factor is introduced to the Sims model. By using the single-parameter exponential smoothing method, the average error of the predicted rolling force is reduced. On this basis, to adapt the model to the discrete data and prevent great errors, a trend adjustment parameter is introduced into the adaptive correction term so that the correction term can be updated accurately in the adaptive process. Finally, a new rolling force model is obtained. The new model achieves a prediction error of 3.75 % when validated with Q345 steel measured data, which is lower than that by the Sims model of 12.68 %. Meanwhile, to further reduce the energy consumption, the multi-objective particle swarm optimization algorithm is used to optimize the rolling schedule, which can reduce the rolling power by 20.07 %–30.04 %, and the reasonable assignment of rolling force during rough rolling stage is realized. The present research can provide scientific guidance for both the construction of a high-precision rolling force model and the optimization of hot rolled plate rolling schedule.

Cortical bone cutting is a common operation in surgery. Studying the potential impact of cortical bone heterogeneity on the processing mechanism will help medical staff to have a deeper understanding of the damage caused by cortical bone cutting (drilling and milling). Therefore, in this paper, the chip formation and removal mechanisms of cortical bone with heterogeneous tissue structures under oblique cutting is studied. The theoretical model of energy release rate under different cutting modes is established and verified by experiments. The results show that when cutting cortical bones with different tissue structures, the energy release rate is different due to the different sizes and distributions of bone units. In the shear cutting and shear crack cutting modes, the energy release rate of the cortical bone structure near the endosteum is higher during the cutting process. It will exceed the fracture toughness of the shear crack cutting and shear fracture cutting modes in advance. The shear crack cutting and shear fracture cutting modes occur at a smaller critical uncut chip thickness. When in shear fracture cutting mode, the energy release rate of the cortical bone tissue near the periosteum will exceed that near the endosteum. The effect of cortical bone structure difference on the critical uncut chip thickness of cutting mode transition is analyzed from the perspective of force and chip morphology. In addition, the machined surface topography is poor when cutting tissue closer to the endosteum cortical bone. This paper provides guidance for analyzing bone tissue damage caused by cutting and optimizing the cutting process.

The rapid expansion of Additive Manufacturing (AM) technologies within the framework of Industry 4.0 raises important questions about their sustainability. Specifically, the widespread use of Material Extrusion (MEx) processes for polymeric materials necessitates a thorough evaluation of the possible balance between performance efficiency and sustainability, highlighting the need for further research into optimizing process parameters to ensure high product quality and reduced energy consumption. The present work focuses on Fused Filament Fabrication (FFF) technology, investigating the relationship between sustainability and print quality. A causal technology model is proposed to elucidate this relationship, underlining the impact of process parameters on defect generation and energy use. A real-time monitoring system for energy consumption measurements was employed to create an energy model that accounts for each component of the CreatBot F430 printer. An image analysis procedure was performed on a special configuration of the HIROX RH-2000 digital microscope to determine the void fraction of each sample. An experimental campaign was conducted, producing single-layer samples in polylactic acid (PLA) following a full factorial plan with four process parameters. A void fraction of up to 18 % was observed, with energy consumption per sample ranging between 638 J and 8843 J. Statistical analysis was performed to assess the impact of each process parameter and to determine operational ranges through the Response Surfaces Method. These results showed good agreement with the predicted conditions, demonstrating the model's effectiveness in supporting decision-making processes in technology selection.

Recent industrial research has looked for techniques that minimize the use of traditional cutting fluids for both economic and environmental concerns. One of the techniques used in machining to limit the use of cutting fluids in metal-cutting that is safe, sustainable, and economical is minimum quantity lubrication (MQL). Further, the lubricating performance of MQL can be enhanced by including solid lubricants. Therefore, the proposed work investigates surface quality, tool wear, chip morphology, and power consumption while drilling aluminium 6082 alloys using HSS drilling tools in various drilling conditions, namely, dry, flood, MQL, and minimum quantity solid lubrication (MQSL). The micron-sized molybdenum disulfide (MoS₂) is mixed with vegetable oil by 1 wt% and applied under the MQSL application. The experimental results showcased that the MQSL application successfully removed chips and burrs to improve the surface quality of holes by an average 3 %–44 % compared to other drilling conditions and resulted in least amount of tool wear. The application of MQSL concluded in lower tool wear from 12 %–56 % comparing to dry, flood, and MQL conditions. Because of its combining impact of lubrication by MoS₂ particles and good cooling efficiency of compressed air, MQSL is effective and concluded in low frictional force at the tool chip and work material area.

Aiming at the problems of severe tool wear and difficulty in ensuring machining surface quality during the cutting process of Ni-base superalloy, a micro-texture design method resembling a shark surface is proposed, which simplifies the skin teeth on the shark surface into a diamond shaped structure with ribs. Different micro-textured samples were prepared using femtosecond laser, and surface wettability characterization and friction and wear experiments were conducted to study the wear reduction and anti wear effects of micro-texture. The parameter combinations with the maximum contact angle and the minimum coefficient of friction were selected. The wear mechanism of YG8 carbide alloy and GH4742, as well as the wear reduction mechanism of microstructure were revealed. Biomimetic cutting tools were prepared and their effectiveness in controlling tool wear, reducing cutting forces, and improving machining quality was verified through milling experiments.

The scan rotation angle (SRA) and build orientation (BO) in the laser powder bed fusion (LPBF) process create unique microstructural features that induce mechanical anisotropy in 316L-stainless steel (SS). To thoroughly investigate their individual and collaborative effects on anisotropy, 316L-SS samples were fabricated with SRAs between adjacent layers (abbreviated as R) of R0 (0°), R45 (45°), R67 (67°), and R90 (90°), and BOs in the XY plane ranging from XY0 to XY90 at intervals of 15°. Tensile testing results revealed that XY0–R67 samples exhibited the highest yield strength (YS), ultimate tensile strength (UTS), and ductility among all samples, while the lowest YS, UTS, and ductility were observed for XY0–R0 samples. Characterization at different length scales was performed to investigate the underlying reasons contributing to mechanical anisotropy. X-ray diffraction (XRD) results indicated that all samples possessed single-phase austenitic structures with varying dislocation densities. The dislocation density had the highest contribution to the YS of LPBF-built 316L-SS in the sequence of XY0–R67 > XY0–R90 > XY0–R45 > XY0–R0. The higher dislocation density in XY0–R67 samples stemmed from the larger residual stresses associated with the higher lattice strains due to the more complex thermal histories and higher cooling rates compared to other cases. A similar phenomenon was also observed for the XY45 BO, which exhibited higher YS due to higher dislocation densities compared to other orientations, regardless of SRAs. Additionally, SRAs significantly influenced the evolution of crystallographic texture, which also affected the YS of LPBF-built 316L-SS.

To unravel the fundamental mechanisms underlying the influence of ceramic phase addition methods on the formation quality and performance enhancement of coatings, the WC/Co-based composite coatings were manufactured on 42CrMo substrate utilizing laser melting deposition technology with different reinforcement phase addition methods grounded in the variable-process alternated overlapping strategy. A comparative analysis was conducted to examine the phase transformations, surface fluctuations, pore defects, microhardness, wear resistance and corrosion behavior. The findings revealed that the in-situ formation of tungsten-carbide phase fell short of the anticipated level due to the physical properties and size constraints of W particles. Notably, the 40 wt% WC particles addition significantly hindered the molten pool fluidity and impeded gas release, leading to pronounced a surface fluctuation of 180.14 μm and a porosity of 31.06 %. In contrast, the direct addition WC particles imparted support, pinning, and strengthening effects, resulting in the optimal microhardness and wear resistance compared to other addition methods, which are 1.46 times and 3.75 times higher than the 42CrMo substrate, respectively. However, an increase in WC particles destabilized the passivation film and promoted the formation of corrosion channels, ultimately exacerbating the corrosion behavior of the WC/Co-based coatings. These insights provide vital theoretical guidance and technical foundations for the adaptive selection of ceramic phase addition methods tailored to the actual working conditions and desired strengthening effects of reinforced coatings for key components.

In comparison to welding in air, the periodic formation of unstable arc bubbles is a significant factor contributing to the unstable mass transfer process during underwater wet welding (UWW). Up to now, there is no ideal method to control droplet transfer and improve arc stability. In this study, the ultrasound-induced method (UIM) was used to regulate the droplet transition behavior and improve the process stability. The behavior features and key mechanisms of arc-bubble and droplet transfer induced by ultrasound were revealed with the employment of highspeed camera and X-ray observation, respectively. The incident angle of ultrasound was taken as a variable to reveal its effects and mechanism of action on the behaviors of arc bubble and droplet transfer, weld formation quality, microstructure, and property of weld joint. The results show that ultrasound-induced a new rising mode of arc bubble, which can significantly reduce the repulsive resistance that come from the bubble rising on the droplet transfer process. Compared with underwater wet welding without ultrasound, the average diameter of molten droplets reduces from 3.2 mm to 1.7 mm, and the droplet transfer frequency increases from 7.8 Hz to 13 Hz as the incident angle of ultrasound increases to 60°. In addition, the weld seam without obvious defects could be produced by UWW with UIM, of which the Variation coefficient of weld reinforcement is reduced from 21.3 to 11.6 and 17.4 at an ultrasonic incident angle of 30° and 45°. With increasing of ultrasound incident angle, it showed that the microhardness of the weld joint has a slight increase. In the heat-affected zone, the microhardness for the joint increased from 290 HV to 320 HV while the incident angle increased to 60°. This research shows that an appropriate incident angle of ultrasound can obtain good-quality joints which has a stable metal transfer process in underwater wet welding.