Journal of Materials Processing Technology最新文献

Oscillating bone sawing is a critical procedure in orthopedic surgery. However, conventional oscillating saw mechanisms often result in excessive sawing forces, which are detrimental to implant fixation and postoperative patient recovery. Therefore, there is an urgent need to design a new oscillating saw mechanism to reduce sawing forces during surgery, including avoiding ineffective impact forces on bone cutting and preventing ploughing forces caused by negative rake angle contact with the workpiece. In this study, an innovative oscillating sawing mechanism is proposed to effectively inhibit the generation and accumulation of impact forces, avoid negative rake angle contact with the workpiece. Oscillating sawing experiments under various cutting conditions demonstrated that the proposed mechanism significantly reduces cutting forces and prevents defects due to crack propagation of the bone and saw teeth damage. The proposed design offers an effective mechanism to achieve small and stable sawing forces in bone sawing surgery, and it inspires tailored oscillating saw techniques for specific machining needs, such as thin deep groove cutting.

While SiCp/Al composites are widely used in engineering applications owing to their excellent material properties, the traditional machining of SiCp/Al composites remains challenging, mainly in terms of poor surface quality and severe tool wear. In this study, a multi-energy field assisted cutting method—pulsed laser-assisted ultrasonic elliptical vibration cutting (PLA-UEVC)—for precision and high-efficiency machining of SiCp/Al composites is introduced. In this method, the intermittent impact cutting effect caused by the tool's ultrasonic frequency elliptical vibration, pulsed-laser-induced material-generated thermoelastic excitation effect, and transient temperature field synergistically work together to enhance the machinability of SiCp/Al composites. Temperature-field simulations were first utilized to simulate the temperature under suitable pulsed laser parameters. Comparative experiments with different volume fractions and particle sizes under different machining methods were conducted to evaluate the advantages of the proposed composite energy field-assisted machining method in terms of chip modulation, surface quality improvement, and tool performance improvement. The experimental results show that multi-energy field assisted cutting achieves better chip control and obtains shorter, easier-to-break chips than traditional cutting, pulsed laser-assisted cutting, and ultrasonic vibration-assisted cutting. The cutting forces of the three industrial-grade SiCp/Al6061 composites with different material properties were significantly reduced (by more than 55 %), with a surface roughness of less than 30 nm obtained for all three composites, effectively suppressing surface defects such as particle failure, thermal damage, and residual height caused by tool vibration. In addition, multi-energy field assisted cutting effectively minimized the abrasive and diffusive wear of the tool and reduced the adhesion phenomenon on the back face of the tool. These findings provide an important theoretical basis and practical machining guidance for multi-energy-field synergistic machining to improve the machinability of SiCp/Al composites.

Spatter serves as a crucial metric for assessing welding stability, with excessive spatter posing significant risks to weld quality, performance, and equipment integrity while also impacting the environment adversely. In oscillating laser-arc hybrid welding (O-LAHW), the spatter exhibits a distinct pattern: an initial sharp decline followed by a gradual increase as oscillation speed rises. Existing research struggles to fully explain this trend due to challenges in developing a precise numerical spatter model. This paper introduces a novel heat flow labeling model and establishes an O-LAHW spatter validation model with 90 % accuracy based on it. Combined with hydrodynamics, this model explores the mechanisms behind spatter formation and suppression based on laser beam oscillation. Firstly, high-speed photography and numerical analysis reveal a third type of spattering in O-LAHW, distinct from spatter caused by keyhole collapse and droplet impact—spatter occurs when liquid metal is expelled from the melt pool due to laser beam oscillation. Secondly, hydrodynamic insights show that laser beam oscillation significantly reduces steam-induced driving force and metal vapor resistance to droplets. Consequently, as oscillation speed increases, the prevalence of the first two spatter types diminishes while the third type becomes dominant. Large-particle spatters decrease while small-particle spatters increase. Finally, by analyzing spatter statistics across various oscillating parameters, we observe a competitive mechanism among the three types of spatters. In non-oscillating welding, Type I spatter predominates; under low-frequency oscillation, Type II gains dominance; in high-frequency oscillation, Type III takes over. Optimal spatter reduction occurs at low-frequency oscillation, achieving a 27.1 % decrease compared to non-oscillating conditions.

Despite various vibration-assisted cutting techniques have been utilized to increase the machining performances of brittle materials, the highly dynamic variations of cutting process quantities lead to the complicated brittle-ductile transition (BDT) mechanism and the formation of undesired vibration marks on the machined surfaces. In this paper, a novel ultra-precision vibration-assisted cutting process, named trapezoidal modulation diamond cutting (TMDC), is firstly proposed for ductile-regime machining of brittle materials with significantly increased BDT cutting depth. By imposing a dedicate trapezoidal locus to the diamond tool, the unique invariable uncut chip thickness and cutting states were achieved for realizing stable vibration-assisted cutting without the formations of vibration marks. Systematic cutting experiments of KDP crystals were carried out to comprehensively investigate the influences of different process parameters on the machining performances of TMDC process. In addition, the underlying mechanisms of machining performance improvements have been discussed under the different combinations of process parameters, based on which the guidelines for optimal process parameter selection are given for increasing the BDT cutting depths. The outcomes of this study contribute to not only improving the ductile machining efficiency and machining quality of KDP crystals, but also help to deepen the understandings of BDT mechanism during vibration-assisted diamond cutting of common brittle materials.

The drilling and cutting of carbon fiber-reinforced epoxy resin matrix composite (CFRP) structural parts is a prerequisite for one-off moulding and assembly connections. However, the thermal ablation effect observed during nanosecond laser hole-making of CFRP results in significant accuracy errors and thermal damage defects in the quality of the holes obtained from the process. To enhance the quality of laser-drilling CFRP holes, a spiral drilling path was employed in this work. The influence of diverse drilling methodologies, encompassing the trajectory of the laser beam, the spacing between scans, and the direction of the suction system's pumping, on the quality of the holes was examined. The impact of these techniques on the precision and integrity of the holes was assessed in terms of their dimensions, the quality factor, the width of the heat-affected zone (HAZ), and the prevalence of microscopic defects. The results demonstrated that when the drilling strategy involves moving the laser beam from the outside to the inside (Scheme I), a scanning spacing of 20 μm, and backward pumping, the optimal micro-hole accuracy and surface morphology, as well as minimal thermal damage defects can be achieved. This study provides a reference for further optimization of the nanosecond laser drilling process.

Tungsten-copper (W-Cu) joints hold immense promise as plasma-facing materials in fusion reactors. However, the inherent immiscibility of W-Cu poses significant challenges in joint fabrication. Here, we introduce an innovative methodology that incorporates laser texture, W surface nano-activation, and subsequent diffusion bonding to fabricate W-Cu joints. Remarkably, the joints achieved exhibit unparalleled mechanical properties, with a peak tensile strength of 201 MPa and a shear strength of 141 MPa, surpassing previously reported W-Cu joints. To gain insights into the underlying mechanisms, we conducted a multiscale analysis utilizing scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and density-functional theory (DFT) calculations. Our findings reveal a unique embedded structure and a metallurgically bonded interface at the W-Cu junction. Furthermore, the diffusion zone at the interface exhibits a fascinating hybrid crystal structure, maintaining a body-centered cubic (BCC) structure in certain regions while displaying a tetragonal crystal structure (with lattice parameters a=b=2.8617, c=3.44) in others. This tetragonal crystal structure formation within the W-Cu diffusion zone remains unexplored in previous literature. In summary, this novel W-Cu bonding approach not only offers a cutting-edge solution for modern manufacturing and fusion energy applications but also lays a solid theoretical foundation for understanding the intricate microstructure-property relationships in W-Cu systems.

Fused silica is an excellent window material widely used in ultraviolet transmission optical system. Crack-free ductile dry grinding is a novel method for the efficient fabrication of fused silica. The grinding temperature field has an important influence on the grinding process. However, most previous studies assumed that the grinding temperature was independent of the wheel’s wear. In this paper, a temperature field model of the ductile dry grinding of fused silica is developed based on wheel wear topographies. Simulated wheel topographies with the same statistical parameters as the realistic wheel wear topographies are reconstructed based on the convolution filtering and Johnson transformation algorithm. The theoretical temperature field is the superposition of the thermal effects induced by effective cutting grain point heat sources extracted from the simulated wheel topographies. The theoretical prediction accuracy of the wheel-workpiece contact zone is validated by an infrared radiation transmission method. This model not only provides opportunity to explore the material removal mechanisms and improve the surface generation quality of fused silica during the wear process of the wheel, but also could be extended to provide the basis for the utilization of grinding heat or prevention of grinding thermal damage for other isotropic materials.

Aluminum alloy 5052 is used extensively in various industries, including aerospace, shipbuilding, and automotive manufacturing. Components made from this alloy often require welding treatments; however, in marine environments, these welds are susceptible to corrosion, which affects their durability and service life. In this study, power-ball combined ultrasonic shot peening (USSP) was used for surface-strengthening 5052 aluminum alloy welds. The resulting surface characteristics and corrosion resistance were examined, and the compared to the untreated sample, the USSP-treated sample showed a shift in the stress state from residual tensile stress (31.4 MPa) to residual compressive stress (−257.5 MPa). Immersion and electrochemical corrosion experiments confirmed that the formation of residual compressive stress and a gradient structure on the surface enhanced the corrosion resistance, which was substantiated by detailed characterization. The corrosion rate of the treated aluminum alloy weld sample (7.18 μm/year) decreased by 72.90 % compared with that of the untreated sample. The study findings indicate that the powder ball combined USSP is a potential method for improving the corrosion resistance of aluminum alloy welds in marine environments.