CIRP Journal of Manufacturing Science and Technology最新文献

Nickel-based superalloys exhibit exceptional suitability for operating in environments characterized by corrosive agents and elevated temperatures. Strategic allocation of this expensive material solely to the functional surface areas yields significant economic advantages. The poor tribological property profile of Inconel 718 can be significantly improved through a boriding process. In this study, the possibility of combining a coating process with boriding technology and in situ heat treatment was investigated. Layers of Inconel 718 were deposited to an austenitic stainless steel using wire-based electron beam cladding (EBC) and subsequently subjected to boriding. Based on results from annealing experiments, boriding treatments were performed at various temperature/time regimens with the aim of inducing in situ age hardening during boriding. The focus was on the investigation of the influence of the temperature/time regime during boriding on the microstructure and hardness, as well as examining the wear and corrosion behavior of the resulting borided layers. The results showed that the desired target hardness range was achieved after in situ aging with all boriding variants. Furthermore, it was demonstrated that boriding significantly improved the wear resistance but decreased corrosion resistance.

Visual inspection in remanufacturing, despite technological progress, is still mainly performed by humans. A rough assessment of the product’s general condition and the dedicated inspection of individual product features or defects is necessary to identify the typically unknown product variant and assess the reusability of a used product and its components. Therefore, a system for automated visual inspection must be flexible and runtime-adaptive, as defects to be inspected in detail may occur anywhere on the product. In the present work, this problem is framed as a view planning problem solved by means of supervised learning and reinforcement learning using a specially developed simulation environment. Three variants of neural networks (PointNet, PointNet++, and Point Completion Network) are compared in the supervised learning case, whereas a deep learning SAC algorithm using the Point Completion Network as network structure is evaluated in the reinforcement learning case. Considering the specific boundary conditions prevailing in remanufacturing, the results are obtained from the use case of electric starter motor remanufacturing. The results show that supervised learning and reinforcement learning are suitable for determining the poses of an acquisition system at system runtime to react to an initially unknown inspection task. Our proposed framework is available open source under the following: https://github.com/Jarrypho/View-Planning-Simulation.

Most metal turning processes utilize cutting fluids. Despite extensive experimental and analytical studies, the mechanisms of chip formation under consideration of a cutting fluid are still not entirely understood. Due to fluid-structure interaction, simulating wet cutting processes for an extended duration has not been feasible. The primary objective of this study is to utilize a simulation approach to provide additional information about the wet chip formation process in contrast to measurement methods, with a view to drawing conclusions. As methodology the Finite-Pointset-Method (FPM) is employed to simulate the chip formation process for dry, flood and specifically high-pressure cooling conditions during machining of carbon steel C45 as well as nickel-based alloy Inconel 718. Due to the increased relative velocity between workpiece and cutting fluid with the use of high-pressure cooling compared to flood cooling, numerical stability issues are present. Initially, the modeling approach to handle high-pressure cooling conditions is described and validated by an impact test. Subsequently the cutting simulation model is presented in detail and verified by measurements. The simulation results of stress, temperature and plastic strain rate fields are used to elucidate the observed discrepancies between various cutting fluid strategies in detail. These findings suggest explanations for the high efficiency of high-pressure cooling such as a decline of hydrostatic stresses or activation of ductile damaging.

Chip breakers are used in turning to improve chip breakage. In standard cutting inserts, they are pressed into the rake face before sintering. However, for specialized tools like profile grooving tools, this pressing is not possible. Instead, a laser preparation process can be applied after grinding the tool profile to create a diverse range of chip breaker geometries. The aim of this investigation is to gain insights into the relationship between the geometric parameters of laser-prepared chip breaker geometries and chip formation. For this reason, experimental turning investigations were conducted with varied chip breaker geometries. Based on these experiments, chip formation was observed for different profile geometries and chip breakers. The findings indicate that the inlet angle, outlet angle, width, depth, and lateral ridges significantly influence chip-breaking behaviour. These results can inform the development of application-specific design for chip breaker geometries.

Adjustable-ring-mode (ARM) laser welding displays great potential for improving the stability of the molten pool and the weld quality of aluminum alloys through the coaxial attachment of a large-sized ring-beam spot. In this paper, the author embarked on a systematic study on the impact of varied core powers, ring powers, and core/ring power ratios on the weld morphology, microstructure, and mechanical properties of Al-Mg alloy during the laser welding process with ARM. The results showed that the core power led to higher depth of penetration, and the superheating of the molten pool it created caused grain coarsening and reduced properties. The ring beam effectively decreased weld spatter and enhanced the surface roughness of the weld. Furthermore, the ring beam was more likely to obtain a wider columnar crystal zone and a more homogeneous grain size distribution. The welded joints possessed higher tensile strength values when ring beam power was increased from 1.5 to 2 kW due to the improvement of surface flatness and porosity defects by the ring beam.

This paper describes development of multi-layer deposition of Ti6Al4V added with 5 at% of Cr, 5 at% of Ni, and 2.5 at% of each Cr and Ni by μ-plasma powder arc additive manufacturing process. It presents findings on their microstructure, porosity, evolution of phases, microhardness, tensile strength, ductility, fracture morphology, fracture toughness, and abrasion resistance. Phase evolution found that α/α’-Ti and β-Ti phases are formed in all the alloys, intermetallic phase Cr₂Ti evolved in Ti6Al4V5Cr and Ti6Al4V2.5Cr2.5Ni alloys whereas intermetallic phase Ti₂Ni is formed in Ti6Al4V5Ni alloy. Their microstructure revealed that addition of chromium and nickel refined grains of their α-Ti and β-Ti phases. Elemental composition of the evolved phases found that at% of chromium, nickel, and vanadium in β-Ti phase is more than the α-Ti phase of the developed alloys. It enhanced their ultimate tensile and yield strength, and microhardness but reduced ductility. It changed the fracture mode from ductile to a combination of ductile and brittle mode possessing large size dimples, micropores, and cleavage facets. It is due to solid solution strengthening, evolution of intermetallic phases Cr₂Ti and Ti₂Ni, and grain refinement of β-Ti and α-Ti phases. Enhanced microhardness and presence of intermetallic phases improved fracture toughness and abrasion resistance of the developed alloys thus imparting them higher resistance to propagation of cracks and abrasive wear.

Automatic electroplating production lines have been widely used in electronics industries to reduce the labour intensity and improve the production efficiency. In the multi-variety and low-volume electroplating production, it is known that the task loading sequence and hoist scheduling are coupled with each other, and they codetermine the production efficiency, while all the existing scheduling methods consider them separately, and thus the optimal production schemes become unavailable. Therefore, this paper develops a Task sequence-Hoist scheduling Coupled Optimization (THCO) model which simultaneously considers the requirements and practical constrains of task sequence and hoist scheduling, having an optimization objective of minimizing the maximum completion time. For this model, a double-layer code is developed and an Improved Salp Swarm Algorithm (ISSA) is developed by introducing three improvement strategies: the random spare strategy which is used to increase the population diversity, the nonlinear adaptive weight strategy which is used to balance the exploration and exploitation capacities, and a golden sine algorithm which is used to improve the convergence rate. Experiments based on 23 benchmark functions are then conducted. The obtained results show that ISSA has better convergence and solving quality than existing algorithms. Furthermore, several production cases prove that THCO can generate production schemes that better meet the requirements of production lines.

Milling robots have the advantage of large workspace and high flexibility compared to machine tools, and are more suitable for machining large and complex surfaces. However, the stiffness of robots is significantly lower than that of machine tools, and they are more prone to chattering. Compared to machine tools, robots mainly occur mode coupling chatter. Analyzing chatter in robots is a great challenge due to the highly flexible and pose-dependent position of the robotic arm. Mode coupling chatter is caused by the most flexible and dominant structural modes of the robot milling system. Available methods are unable to identify the structural modal parameters of a milling robot at all poses in the actual working state. This paper proposes a modal analysis method for robots, which can realize the automatic traversal of the pose of the milling robot and the automatic identification of modal parameters. This paper analyzes the robot multi-joint flexibility characteristics, spatial structure characteristics, and machining vibration characteristics, correlates the joint motor control system and current power characteristics, finds the correlation between the current information and the vibration information, and identifies the modal frequency through the current signals, and realizes the modal frequency identification in the entire workspace. This method is capable of output-only complete mode shape identification, can quickly analyze the main vibration modes, and is of great significance for the study of robot milling chattering.

Wire arc additive manufacturing (WAAM) is increasingly gaining attraction from researchers and industries worldwide due to its low cost and the ability to produce intricate parts in a shorter time. In this study, the bimetallic wall of aluminium alloys (ER5356/ER4043) is fabricated by cold metal transfer based WAAM technique using two deposition directions (unidirectional and bidirectional) and three current combinations (115 A/90 A, 120 A/95 A, 125 A/100 A). The effect of deposition direction and current on microstructure evolution, mechanical properties, and residual stress has been investigated. Experimental results displayed better properties in bi-directional wall build at a current combination of 115 A/90 A. This is confirmed by optical microstructure as well as field emission scanning electron microscopy, which shows equiaxed grains on the ER4043 layer, fine grains on the ER5356 layer, and columnar-fine grains at the interface of the bi-directional wall while discontinuous dendritic grains is displayed in ER5356 layer of unidirectional wall. Energy dispersive spectroscopy analysis indicates a main difference in weight percentage for Si and Mg contents at the interface layer of the bidirectional wall than the unidirectional wall, with X-ray diffraction analysis specifying the intermetallic compounds like α-Al, Al₁₂Mg₁₇, Mg₂Si, AlMg, and Al_3.21Si_0.47 in both depositional directions. Tensile strength at the interface layer of the bi-directional wall surpasses the tensile strength of the unidirectional wall's interface layer, with fracture morphology indicating ductile fracture in all specimens. The microhardness test reveals an increase in hardness in the transverse direction at the current combination of 115 A/90 A and also in the bidirectional deposition wall compared to the unidirectional wall. Bidirectional deposition has generated less residual stress than unidirectional walls.

Due to the poor surface characteristics of additively manufactured parts, the necessity for post-process surface enhancement is crucial. Among the prevalent post-processing techniques, the acoustic cavitation-based surface finishing technique has recently emerged. Despite a considerable amount of focused research on the material removal mechanisms of this technique, less attention has been devoted to addressing its limitations associated with enhancing the process capability towards achieving a better surface finish. The driving force behind the acoustic cavitation technique is the bubble implosion through cavitation streaming, and the cessation of the acoustic cavitation streaming beyond a certain length is the main limitation. It has restrained the process capability towards finishing both external and internal surfaces. Hence, this research aims to unravel novel ways of employing the acoustic cavitation-generating parameters and achieving better-quality surface finishing of additively manufactured (AM) components. A study has been conducted on different AM materials, including Inconel 625 and aluminum alloy, by introducing various methods associated with acoustic amplitude, working mediums, temperature, and external vibration. The results reveal a significant reduction in average surface roughness for both materials. The topographical and morphological observations confirm the qualitative improvement on the surfaces. In addition, the conical bubble structures that frame the acoustic cavitation streaming are elucidated by implementing high-speed imaging techniques, and their enhancement at different parametric conditions is delineated. Henceforth, the findings suggest a notable insight into the potential of the employed approaches in enhancing the acoustic cavitation streaming for achieving a better surface finish of AM components.