Journal of Manufacturing Processes最新文献

Riveting has a wide range of advantages in improving the performance of composite connections, however, it is highly likely to cause damage to the composite structure. Therefore, an experimental study was conducted to assess the damage behaviors of the carbon fiber reinforced polymer (CFRP)/CFRP blind riveted joint. Mechanical performance of joints was also evaluated experimentally. Furthermore, failure modes were exhaustively discussed. The influences of the rivet shank length on both the riveting damage and the mechanical performance were also investigated. The results demonstrated that: the surface bearing damage occurred on the first ply and was mainly caused by the pressure of forming the riveted head along the rivet shank axial. Serious damage occurred in the upper plies near the riveted head due to the radius expansion of the rivet shank. The damage modes were affected by the angles of the fiber laying direction and the rivet shank. The grooved blind riveting formed a localized protruding area around the periphery of the holes and caused less riveting damage. The failure modes of the tensile specimens were all shear failure, and the failure modes of the pull-off specimens were characterized by laminate fracture around the rivet holes, which subsequently led to rivet pull-off failure. It is worth emphasizing that the pull-off damage load and failure load of grooved blind riveted specimens were higher than those of general blind riveted specimens, while the grooved blind riveting reduced the tensile resistance.

This study introduces an innovative technique known as fast-frequency double pulse wire arc metal additive manufacturing (FFDP-WAAM). This method employs periodic fluctuations in arc plasma and force to enhance the stirring effect within the molten pool, resulting in the fragmentation of β grains and the formation of finer prior-β grains. The microstructure primarily comprises α', attributed to the high cooling rates and minimal heat accumulation. Compared to the conventional gas tungsten arc welding-based WAAM (CGT-WAAM) process, FFDP-WAAM significantly reduces α-variant selection, thereby achieving a more uniform α phase orientation distribution. Additionally, ultrasonic vibration in the FFDP-WAAM process facilitates recrystallization and mitigates residual strain. The tensile strength and elongation of the FFDP-WAAM specimens reached 939.2 MPa and 9.0 %, respectively, whereas the CGT-WAAM specimens showed a lower tensile strength of 830 MPa and elongation of 9.2 %. The enhanced strength, fatigue life and microhardness of Ti-6Al-4V produced by FFDP-WAAM is ascribed to the refined grain-size distribution. Furthermore, the low Schmid factor (SF) distribution and the stable triangular structure of Category I α-clusters are anticipated to contribute to the increased strength of the FFDP-WAAM-fabricated wall.

Titanium alloy materials are increasingly used in consumer products such as mobile phones and computers. Currently, manufacturers use ultra-high speed machining techniques to process titanium alloy materials to ensure high production efficiency. However, under the high spindle speed of 8000 rpm and a large feed rate of 4500 mm/min, the cutting speed of a 10 mm diameter milling tool reaches up to 251 m/min, which is significantly higher than the traditional cutting speed for titanium alloys (90 m/min). This ultra-high-speed cutting condition inevitably leads to a reduced tool life, consequently increasing manufacturing costs. Therefore, this paper focuses on studying methods to improve the cutting performance and tool life in titanium alloy ultra-high speed milling. First, failed milling tools on the titanium alloy processing production line were detected, and the failure modes and wear mechanisms of the tools under ultra-high speed milling conditions were analyzed. Based on this, a milling simulation model was established and calibrated through milling experiments. Then, simulation experiments were designed using the response surface methodology to reveal the impact of key tool geometric parameters on cutting performance, and the geometric parameters of the milling tool were optimized. Finally, based on the optimization results, milling tools were prepared and cutting performance and tool life experiments were conducted. Compared with the unoptimized milling tools, the optimized milling tools have significantly improved cutting performance and tool life, with cutting force reduced by 40 %–50 % and average tool life increased by 69.6 %.

This paper aims to explore the evolution of microstructural parameters induced during the cutting of Ti6Al4V alloy (TC4). The microstructure characteristics of the workpiece material is directly tied to its mechanical response during machining. During TC4 cutting, microstructure evolution is observed as a result of severe plastic deformations. The characterization of this phenomenon has significant interest from both academia and industry. In this work we present a developed modeling technique which combines the Particle Finite Element Method (PFEM) with incremental homogeneous field distributions. First, the PFEM is extended to perform a thermo-mechanical analysis capable of capturing the material responses of TC4 during orthogonal cutting. To generate serrated chips, an appropriate strain softening-based constitutive plasticity model i.e., TANH (Hyperbolic TANgent) is utilized. The PFEM’s validity is checked through comparison with available experimental results in terms of chip shapes and cutting forces. Second, the evolution of microstructural parameters such as dislocation density, vacancy concentration, dynamic recrystallization (DRx) grain size, and hardness is incrementally developed and incorporated into the PFEM using internal state variables as homogeneous field distributions. The Johnson–Mehl–Avrami–Kolmogorov (JMAK) model and Hall–Petch equation are applied for predicting grain size and hardness, respectively. The parameters of the corresponding models are modified for TC4 to accurately capture their alterations. Lastly, the predicted results of the microstructure evolution in serrated chips and machined surfaces, including average grain size and hardness, are compared with experiments, demonstrating good agreement. This implies that the PFEM combined with microscale schemes can reliably simulate the machining process of the TC4.

In this study, 5 different Al2024/FRP/Al2024 metal stacked composites were produced and their machinability by abrasive water jet machining (AWJM) method was investigated. Synergistic interaction of these materials offers new and improved properties, but machinability remains an area of research due to widely varying mechanical properties. The effects of different stacking and traverse speed on hole quality in cutting with AWJM were determined. The hole diameter deviation (HDD) ratio, kerf, delamination, hole circularity, and surface morphology were analyzed. Result of the current study showed that the increase in traverse speed caused an increase in the HDD ratio, in the visibility of the cutting starting point, in the deviation of circularity, and in the bore-hole damage formation. In all stacks with CFRP, an average deviation of 5 % at the hole entrance and 4 % at the hole exit occurred at a traverse speed of 1000 mm/min. At 400 and 600 mm/min traverse speeds, an average of 2.8 % deviation occurred at the hole entrance and an average of 2.13 % at the hole exit. This proves that the traverse speed has a significant effect on the hole diameter. In addition, as the traverse speed decreased, it was noticed that the layers separated from each other, causing delamination, and therefore the thickness of the FML increased. Different defects were observed to occur in FRP structures used in FML with SEM analysis. Intralayer defects were more dominant in GFRP laminate, whereas interlayer defects were found to form in CFRP laminate.

The deformation prediction and control of thin-walled components are receiving increasing attention. Residual stress is an important factor affecting the deformation of workpieces. A deformation prediction model considering machining residual stress is proposed based on the theory of thin plate bending. The introduced machining residual stress was calculated using contour method and XRD diffraction method. The variation of residual stress after coupling was derived using the layer shifting method, and the influence of neutral layer position variation on residual stress redistribution was analyzed. The accuracy of the model was verified through corresponding experiments and finite element simulations, with relative errors of 12.1 % and 50.2 %, respectively. In addition, the deformation of rectangular and complex shaped thin-walled parts was compared through finite element simulation, which extended the application scope of thin plate bending theory. In addition, ten material removal processes were simulated and calculated using the life and death unit method, and the optimal processing technology was confirmed. Corresponding experiments were conducted to verify the results, with a maximum relative error of 17.6 %. In addition, the residual stress was reduced by multiple deep cooling treatments and composite ultrasonic vibration aging methods, with a maximum residual stress reduction rate of 25.1 %. Finally, the overall deformation of the workpiece was comprehensively characterized, and the flatness of the four different surfaces was reduced to 22 μm, 23 μm, 26 μm, and 21 μm respectively through three deep cooling treatments and ultrasonic vibration.

Fabrication of particle-reinforced metal matrix composite sheets using twin-roll casting (TRC) encounters quality challenges in the cast product, constraining its industrial viability. The present study investigates the effect of variable sheet thicknesses (3 mm, 4 mm and 5 mm) on the quality of composite sheets fabricated through TRC. The effects of sheet thickness on the thermal-fluid behavior of composite sheets in the TRC process were modeled using the finite element method. The model was validated by comparing the calculated inter-lamellar spacing with those measured through the experiment. As the sheet thickness increases, heat flux along the roll surface increase and colling rate decreases at a constant inlet temperature. Therefore, lowering the inlet temperature with increased sheet thickness helps to increase the cooling rate from the roll surface. Hence, an increased sheet thickness requires a lower inlet temperature to fabricate a composite strip successfully. The optimized inlet temperatures of 836 K, 831 K, and 826 K were suggested for fabricating Al-Mg₂Si composite sheets of 3 mm, 4 mm, and 5 mm thickness, respectively. The thicker sheet experiences a more pronounced variation in velocity vector, suggests that the thinner sheet (3 mm) fabrication is more favorable for continuous casting than a thicker sheet (5 mm). A cooling rate of less than 50 K/s for a 3 mm thickness sheet in TRC process leads to incomplete solidification, posing a risk of sheet breakout during the continuous casting operation. Increasing the sheet thickness from 3 mm to 5 mm increases tendency of porosity formation and centreline shrinkage from 3.8 % to 10.5 %.

This study presents an experimental investigation of vibration-assisted machining (VAM) techniques for monocrystalline silicon. The author introduces a novel high-frequency two-dimensional vibration-assisted machining system which is used to conduct slot milling experiments using ultrasonic high-frequency. For comparison, a low-frequency non-resonant vibration-assisted machining system is also used in the experiments. The effects of machining parameters, including feedrate, cutting speeds, and vibration parameters, including vibration modes and amplitudes, on the machining performance are thoroughly investigated. The surface roughness, edge chipping generation, and tool wear under various machining conditions are characterised using scanning electron microscopy (SEM). The results show that, under specific machining and vibration parameters, a nanometric surface roughness (Ra) can be achieved. The ultrasonic vibration-assisted micro-milling (UVAMM) system is found to offer better surface quality, improved edge quality, and reduced tool wear. This study demonstrates that vibration-assisted micro-milling is a valuable technique for producing silicon components at scales ranging from a few microns with a nanometric surface finish with an improvement of 144 % compared to Conventional Machining (CM). The proposed 2D UVAMM system in this paper also provides valuable insight into the direction for utilizing 2D vibration-assisted machining systems to achieve superior machining results.

The deep and narrow groove structure has wide applications in micro-devices such as high-frequency circuits, micro heat pipes, microchannels, etc.. It has been involved in various fields, including aerospace, electrocommunication, and medicine. However, as the deep and narrow groove structure shrinks, the processing accuracy and surface quality become challenging factors limits its further development. The radius of the micro-milling cutter edge plays an important role in precision and surface quality. Therefore, this paper conducts a systematic experimental study on the edge radius using custom-made PCD micro-milling cutters and commercially available cemented carbide milling cutters. This study investigated the influence of three different cutting-edge radius, 1.73 μm, 2.39 μm, and 2.97 μm, of PCD micro-milling cutters and varying feed rates per tooth on milling surface morphology and burr formation. A comparison was also made between the cutting performance and machining quality of PCD micro-milling cutters and cemented carbide micro-milling cutters. The results indicated that the machining quality of deep, narrow grooves is significantly related to the cutter's cutting-edge radius, tool material, and milling parameters. PCD tools with smaller cutting-edge radii produced micro-grooves with an optimal surface roughness of approximately 40 nm and minimal surface burrs under the same parameters. Therefore, using PCD micro-milling cutters with a smaller cutting-edge radius is crucial in improving the quality of deep and narrow groove machining.

Ball-end mills are commonly employed for semi-finishing and finishing of complex surfaces, widely utilized in the energy, automotive, aerospace and other industries. During surface machining, cutter workpiece engagement (CWE) area of the ball-end mill continuously varies with surface characteristics and the tool paths. Additionally, the actual position of the tool involved in cutting also changes, leading to uneven wear distribution on the ball-end mill, making tool wear prediction and evaluation challenging. In this paper, a discretization calculation method of tool path length for surface machining is proposed based on PowerMill post-processing development. The linear cutting length of tool path for each corresponding tool posture is calculated, and the approximate calculation model of average milling distance of single tooth for cutting edge element is established. The correlation mapping between NC machining program, tool posture and cutting workload of cutting edge element is realized. A tool wear model that considers effective cutting distance is developed, enabling the prediction of wear distribution along the flank of the ball-end mill under the surface machining conditions. Comparative experiments were conducted on tool wear under different feed directions during curved surface machining. The experimental results confirm the effectiveness of the proposed ball-end mill wear prediction method.