Journal of Materials Processing Technology最新文献

This study investigated the complex thermal accumulation characteristics and their effects in the time and spatial domains during the preparation of complex Nitinol (NiTi) alloy structures using laser powder bed fusion (LPBF) technology. The findings reveal a pronounced size dependency phenomenon when the formed dimensions fall below 2 mm. Specifically, a reduction in formed size leads to a marked surge in element loss, a heightened prevalence of internal defects, and a corresponding decline in both mechanical and functional properties. Small-sized (<0.5 mm) samples have significant thermal accumulation due to their fast heating and slow cooling rates, requiring control of heat input. Medium sized (0.5–2 mm) samples have significant temperature gradients as a result of their rapid heating and cooling rates, requiring control of high-temperature residence time. Large sized (> 2 mm) samples necessitate the insulation measures to reduce thermal stress, owing to their sluggish heating and rapid cooling characteristics. Therefore, we developed a model to evaluate the thermal history characteristics of parameters or design schemes and compensate or eliminate heat accumulation during the machining process to balance the thermal history characteristics. This model can also be combined with a thermal field detection system to develop real-time thermal management and control modules for processing. The key to eliminating size-dependency effects is to homogenize the microstructure. A single aging heat treatment (773 K for 0.5 h with air cooling) can effectively homogenize the structure and eliminate size dependence.

The thermal deformation in the process of thin-walled metal fin processed by wire electrical discharge machine (WEDM) is almost unavoidable, which restricts the application of wire electrical discharge machining in the precision machining of thin-walled parts. In this study, a new process of thermal bending deformation regulation by laser-induced shockwave of wire electrical discharge machining thin-wall fin was proposed to obtain low/no deformation thin-wall parts. The thermal deformation of thin-wall In718 metal processed with different wire electrical discharge machining parameters was calibrated, and the law between the thermal bending and the process parameters was obtained. The thermal ablation and laser shock thermal deformation regulation model was established to accurately describe the stress distribution and deformation behavior of thin walls. For In718 thin-wall fin with different thicknesses, the thermal bending deformation could be regulated by laser-induced shockwave. After adjustment, the warpage of all thin walls was only −0.174μm at the lowest, and the thermal deformation could be reduced by 98.35 % at the highest. Laser shock improved the surface integrity of thin walls, increased the surface hardness to 433.9HV, increased by 46.84 %; laser shock also reduced the surface roughness of thin walls to a maximum of 2.67μm, a decrease of 33.58 %. In addition, laser shock could reduce the number of large-size grains, increase the number of twins, refine the impact surface grains to a certain extent, and the particle size was reduced to 7.64μm, which was reduced by 45.62 %.

Conventional polishing methods face significant challenges for achieving excellent performance on complex surfaces. The magnetorheological shear thickening polishing (MRSTP) method, with its dual-stimulus response of shear thickening and magnetization enhancement, offers an effective solution for polishing complex surfaces. However, existing models fail to elucidate the cross-scale material removal mechanisms in MRSTP owing to the coupling of magnetic and flow fields. In this study, a comprehensive model was proposed to address the the challenge of predicting the cross-scale material removal rate (MRR) in MRSTP for complex surfaces. Analytical and finite difference methods were employed to solve the pressure distribution during the MRSTP process using magnetohydrodynamics. By incorporating the pressure distribution, an MRR predictive model was developed for arbitrary points on the workpiece surface based on the indentation theory for active abrasive grains. The material removal mechanism was explored by considering elastic and plastic deformation under fluid pressure. The experimental validation showed a relative error of 14.9 % between the theoretical and experimental MRR. Experiments on aero-engine blade tenons demonstrated that the established MRR model is well suited for application to complex surfaces. This study ultimately reveals the material removal mechanism of MRSTP with coupled magnetic and flow field, providing a new foundation for predicting MRR on complex surfaces.

With the improvement of application requirements, the combination of precise shape and high performance of tube components has become a burning issue. This work investigates the free-bending process of 6063 aluminum alloy tubes using cross-scale numerical modeling. The cross-scale framework integrates macroscopic finite element model (FEM) and crystal plasticity finite element model (CPFEM) through strain history. CPFEM exhibits excellent agreement with the macroscopic FEM and experimental results for both the Mises stress and texture evolution. Predictions indicate that as bending deformation increases, the volume fractions of the initial Cube texture decrease, while the Goss texture component increases. The overall texture strength continuously decreases. Meanwhile, slip mode plays a critical role in texture evolution, causing similar trends in the inner and outer bend regions. Additionally, the findings from the cross-scale simulation accurately predict the detailed texture evolution of the 6063 aluminum alloy tube under various feeding speeds. The development of Goss texture in various forming regions and the formation of substructures within Goss-oriented grains are primary factors contributing to reduced tube formability, which could illustrate the primary mechanisms for variation in tube bendability effectively. The proposed cross-scale method lays the foundation for research on complex spatial tube components as well. Moreover, cross-scale simulation facilitates the prediction of macroscopic deformation and microstructural evolution in critical regions of tube components, allowing for the optimization of bending processes based on cross-scale simulation results.

Forming limit curve (FLC) is an essential criterion for evaluating the formability of fiber metal laminates (FMLs) in mass fabrication. However, conventional methodologies are unable to predict inner fiber failure, very sensitive to wrinkling defects, resulting in low measurement accuracy and stability. Hence, a novel dual-stage failure criterion considering the progressive failure of fiber and metal layers has been developed and validated by utilizing a notch-pattern sample and forming of typical thin-walled structure, with four typical categories of glass laminate aluminum reinforced epoxy (GLARE). The Nakajima tests of a series of notch-pattern and conventional pattern specimens with different widths were conducted in this study, demonstrating the superiority of wrinkling and delamination prevention of the notch-pattern by enhancing 22.84 % stress triaxiality and reducing 39.51 % compress strain in the edge area. Notably, punch reaction force and strain field analyses unveiled a mutation phenomenon indicative of premature fiber failure while the aluminum remained intact, which was also verified by numerical and interrupted methods. Furthermore, the acoustic emission in-situ method was adopted to monitor the progressive damage evolution of uncured GLARE in the Nakajima test, providing solid support for the occurrence of fiber failure at the mutation site. Leveraging these mutations, a list of dual-stage forming limit curves was devised to quantify the progressive damage behavior of uncured GLARE under biaxial tensile conditions. Finally, the practical application of this novel dual-stage forming limit curve methodology was demonstrated in the manufacturing process of a box-shaped part, serving as a proof of concept for its effectiveness. This study offers a foundational guideline for characterizing the intrinsic failure mechanisms of fiber metal laminates, particularly internal fiber failure under various strain conditions, thereby enhancing predictive accuracy.

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.