Minimum quantity lubrication (MQL), which considers the cost, sustainability, flexibility, and quality, has been actively explored by scholars. Nanoadditive phases have been widely investigated as atomizing media for MQL, aimed at enhancing the heat transfer and friction reduction performance of vegetable-oil-based biolubricants. However, the industrial application of nano-enhanced biolubricants (NEBL) in grinding wheels and workpiece interfaces as a cooling and lubricating medium still faces serious challenges, which are attributed to the knowledge gap in the current mapping between the properties and grindability of NEBL. This paper presents a comprehensive literature review of research developments in NEBL grinding, highlighting the key challenges, and clarifies the application of blind spots. Firstly, the physicochemical properties of the NEBL are elaborated from the perspective of the base fluid and nanoadditive phase. Secondly, the excellent grinding performance of the NEBL is clarified by its distinctive film formation, heat transfer, and multiple-field mobilization capacity. Nanoparticles with high thermal conductivity and excellent extreme-pressure film-forming properties significantly improved the high-temperature and extreme-friction conditions in the grinding zone. Furthermore, the sustainability of applying small amounts of NEBL to grinding is systematically evaluated, providing valuable insights for the industry. Finally, perspectives are proposed to address the engineering and scientific bottlenecks of NEBL. This review aims to contribute to the understanding of the effective mechanisms of NEBL and the development of green grinding technologies.

In this study, a strategy based on the particle swarm optimization (PSO) algorithm is developed to control the microstructures of a Ni-based superalloy during hot forging. This strategy is composed of three parts, namely, material models, optimality criterions, and a PSO algorithm. The material models are utilized to predict microstructure information, such as recrystallization volume fraction and average grain size. The optimality criterion can be determined by the designed target microstructures and random errors. The developed strategy is resolved using the PSO algorithm, which is an intelligent optimal algorithm. This algorithm does not need a derivable objective function, which renders it suitable for dealing with the complex hot forging process of alloy components. The optimal processing parameters (deformation temperature and strain rate) are obtained by the developed strategy and validated by the hot forging experiments. Uniform and fine target microstructures can be obtained using the optimized processing parameters, which indicates that the developed strategy is effective for controlling the microstructural evolution during the hot forging of the studied superalloy.

Development of artificial joints is a great progress for joint replacement operations of human being, but the short longevity of prostheses has concerned both industries and researchers since the advent of modern implants. Thus, continuous improvements have been made alongside the clinical applications. The methodologies to inspect the potential properties of new designs have also seen many advances. The test machines have evolved from easy pin-on-disk configuration to the modern joint simulator. Besides, various wear traces provided by testing machines are investigated greatly, and multi-directional files are recommended as motion profiles for in vitro testing. The typical testing parameters, like sliding speed or loading profile, are discussed in this article, and their working mechanisms are described in detail. Meanwhile, the calf or bovine serum has been regarded as the gold standard for testing lubricant, and the future trend of fluid will be focused on investigating the effects of lubricant composites on the tribological properties. Hard particles and proteins are discussed as well, and their effects on the wear mechanisms are the focus. Finally, various approaches to measure the wear rate, wear factor and the thickness of lubricant film are presented, and suggestions are given for the development in future.

To conduct a reliability analysis for mechanical components, it is necessary to consider the combined influence of strength deterioration and dynamic loads. An efficient method based on subset simulation is proposed in this paper to analyze time-variant reliability by considering the strength deterioration of mechanical components in a continuous system. A gamma process is used to describe the deterioration of system strength. A model for time-variant reliability considering strength deterioration is constructed for a continuous system. A representative example and tubular cantilever structure are assessed to demonstrate the efficiency and accuracy of the proposed method. The reliability probability examples were analyzed using a first-order reliability method and benchmark results for the proposed method were derived using direct Monte Carlo simulation (MCS). The results of the proposed method and MCS are consistent, indicating that the proposed method is an effective reliability analysis method for evaluating small failure probabilities in a continuous system subjected to strength deterioration and dynamic loads.

The extrusion-based additive manufacturing (EAM) technique is recently being employed for rapid production of metals and ceramic components. This technique involves extruding the metal or ceramic material in solid powder form mixed with a binder (i.e., an expendable viscous fluid), which is removed from the part after 3D printing. These technologies rely on the large design freedom allowed and the cost efficiency advantage over alternative metal additive manufacturing processes that are based on high energy beams, such as laser or electron beams. The EAM of metals and ceramics is not yet widespread, but published scientific and technical literature on it is rapidly growing. However, this literature is still less extensive than that on the fused deposition modeling (FDM) of plastics or the selective laser melting (SLM) of metals. This paper aims at filling this gap. FDM and powder injection molding are identified as preceding or enabling technologies for EAM. This paper systematically reviews all aspects of the feedstock EAM processes used for production of complex-shaped parts. The unique characteristics and advantages of these processes are also discussed with respect to materials and process steps. In addition, the key process parameters are explained to illustrate the suitability of the EAM process for diverse application domains.

Ti-6Al-4V has a wide range of applications, especially in the aerospace field; however, it is a difficult-to-cut material. In order to achieve sustainable machining of Ti-6Al-4V, multiple objectives considering not only economic and technical requirements but also the environmental requirement need to be optimized simultaneously. In this work, the optimization design of process parameters such as type of inserts, feed rate, and depth of cut for Ti-6Al-4V turning under dry condition was investigated experimentally. The major performance indexes chosen to evaluate this sustainable process were radial thrust, cutting power, and coefficient of friction at the tool-chip interface. Considering the nonlinearity between the various objectives, grey relational analysis (GRA) was first performed to transform these indexes into the corresponding grey relational coefficients, and then kernel principal component analysis (KPCA) was applied to extract the kernel principal components and determine the corresponding weights which showed their relative importance. Eventually, kernel grey relational grade (KGRG) was proposed as the optimization criterion to identify the optimal combination of process parameters. The results of the range analysis show that the depth of cut has the most significant effect, followed by the feed rate and type of inserts. Confirmation tests clearly show that the modified method combining GRA with KPCA outperforms the traditional GRA method with equal weights and the hybrid method based on GRA and PCA.

A physical-based constitutive model was developed to model the viscoplastic flow behavior and microstructure evolution of AZ80 magnesium alloy during the hot working process. The competing deformation mechanisms, including work hardening, dynamic recovery, and dynamic recrystallization, in an isothermal compression environment were considered in the model. The internal state variables, including the normalized dislocation density and recrystallized volume fraction, were incorporated into the model to articulate the microstructure evolution during hot deformation. The kinetic condition critical for dynamic recrystallization, considering the effects of the deformation temperature and strain rate, was obtained by employing both the Poliak-Jonas criterion and Zener-Hollomon parameter. Microstructure observations indicate that the recrystallized volume fraction increases with decreasing Z parameter at constant strain, which is consistent with the predicted kinetics model. Based on the developed model, a good correlation was also obtained between the predicted and experimental flow stress. The results indicate a good predictability of the model in describing the hot deformation behavior and microstructure evolution of AZ80 magnesium alloy.

In this study, 2% Fe and 3% Al co-doped ZnO nanoparticles were synthesized using a hydrothermal method under high magnetic field (HMF). The influences of HMF on the structural, optical, and ferromagnetic properties of Fe and Al co-doped ZnO nanoparticles were characterized and analyzed. The single-phase wurtzite structure of the synthesized samples was confirmed using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy analysis. The application of HMF decreases the particle size of the spherical nanocrystal as observed by scanning electron microscopy (SEM). Optical analysis indicated that the absorption edge shifted towards a higher wavelength (red shift). The nanoparticles synthesized under the HMF exhibited high room temperature ferromagnetism (RTFM) performance because of the high oxygen vacancy (VO) content as revealed by X-ray photoelectron spectroscopy (XPS), which was in agreement with the prediction of the bound magnetic polarons theory.

Creep age forming (CAF) is an advanced forming technology used for manufacturing large complex integrated panel components. However, in creep aging (CA), unlike in sole creep or aging procedure, the dislocation movement and the precipitation process occur simultaneously, leading to difficulty in understanding of the dynamic interplay between these two phenomena. In this work, taking 7050 Al alloy, a typical Al-Zn-Mg-Cu alloy, as the test material, an experimental scheme combining pre-deformation, artificial aging (AA), and tensile/compressive CA is designed to decouple and reveal the dynamic interaction mechanism of both phenomena. From AA experiments, the static interaction between dislocations and precipitates is studied, and then their dynamic interactions in CA and each evolution are comparatively investigated. The research shows that both total strain and strain rate increase with the increase in pre-deformation in tensile and compressive CA. However, the total creep strain in compressive CA is larger than that in tensile CA. In additional, the more the dislocations are induced, the sparser and more heterogeneous the overall distribution of precipitates becomes. For dynamic interplay, in the first stage of CA (I), under thermal-mechanical loading, the GP zones and η′ phases gradually nucleate and grow, while the effect of dislocation multiplication is dominant compared with dislocation annihilation, leading to an increase in total dislocation density. Soon, the dislocation movement is gradually hindered by tangling, pile-up, and the precipitates that have grown on the dislocation lines, this decreases the mobile dislocation density and results in a significant decrease in creep rate. In the second stage (II), the precipitates grow further, especially those lying on the dislocation lines; the effects of pinning and hindrance are enhanced until the dislocation multiplication and annihilation reach a dynamic equilibrium, and the total and mobile dislocation densities tend to be roughly unchanged, thus, the creep rate remains relatively constant in this stage.

Industrial robots are widely used in various applications such as machining, painting, and welding. There is a pressing need for a fast and straightforward robot programming method, especially for surface-based tasks. At present, these tasks are time-consuming and expensive, and it requires an experienced and skilled operator to program the robot for a specific task. Hence, it is essential to automate the tool-path generation in order to eliminate the manual planning. This challenging research has attracted great attention from both industry and academia. In this paper, a tool-path generation method based on a mesh model is introduced. The bounding box tree and kd-tree are adopted in the algorithm to derive the tool path. In addition, the algorithm is integrated into an offline robot programming system offering a comprehensive solution for robot modeling, simulation, as well as tool-path generation. Finally, a milling experiment is performed by creating tool paths on the surface thereby demonstrating the effectiveness of the system.

How to form high-quality transverse inner ribs through power spinning is a key issue for complicated integrated curved generatrix parts with transverse inner ribs. In this study, the forming characteristics and laws during the power spinning process were investigated using a finite element simulation based on the orthogonal design method. The results show that the transverse inner rib distributes homogeneously along the circumferential direction but inhomogeneously along the generatrix direction. Depressions occur easily in the middle zone of the rib (MZR). The roller nose radius is the most significant parameter of the MZR underfill degree. A larger roller nose radius is helpful to decrease the MZR underfill degree. Furthermore, the preformed billet thickness also plays a vital role in the underfill degree of the front zone of the rib and the back zone of the rib, as well as the depression degree of the outer surface of the rib. By combining the rib-filling characteristics and laws, the optimized forming process window for obtaining high-quality inner ribs was obtained by regression analysis, thus laying a basis for improving the forming quality of curved generatrix parts with transverse inner ribs in power spinning.