International Journal of Machine Tools & Manufacture最新文献

Tool condition monitoring (TCM) during mechanical cutting is critical for maximising the utilisation of cutting tools and minimising the risk of equipment damage and personnel injury. The demand for highly efficient and sustainable machining in modern industries has led to the development of new processes operating under specific conditions. Real-world datasets obtained under harsh cutting conditions often suffer from intense interference, making the anti-interference capabilities of TCM methods crucial for effective industrial applications. Previous literature reviews on TCM have focused on theoretical methods for monitoring tool wear and breakage. However, reviews of the scientific methodologies and technologies employed in TCM for industrial production are limited. The lack of scientific understanding relevant to the monitoring of cutting tools in industrial production should be addressed urgently. The current data processing, feature dimensionality reduction, and decision-making methods utilised in TCM may not adequately fulfil the real-time and anti-interference demands. The TCM methods also face the challenges of small sample sizes and imbalanced data during real-world dataset processing. Therefore, this study conducts a systematic review of TCM methods to overcome these limitations. First, the theoretical guidelines for the application of TCM methods in industrial production are provided. The sensing system, signal processing, feature dimensionality reduction, and decision-making methods for TCM methods are comprehensively discussed in terms of both their advantages and limitations for applications in industrial production. Considering the effects of real-world datasets with small samples and imbalanced data caused by the harsh environment of a real factory, a systematic presentation is proposed at the data, feature, and decision levels. Finally, the challenges and potential research directions of TCM methods for industrial applications are discussed. A research route for smart factory-oriented machining system management is proposed based on published literature. This review bridges the gap between theoretical research and the industrial application of TCM techniques in industrial production. Prospective research and further development of TCM systems will provide the groundwork for establishing smart factories.

In high speed milling, interrupted cutting conditions can lead to period doubling chatter vibrations. While many studies have already confirmed that the use of helical tools can effectively shrink or remove these regions of unstable cutting, none of them has provided clear guidance to select the minimum helix that completely cancels the period doubling lobes. This study addresses this gap by introducing a novel analytical formula for a critical tool helix pitch: if the helix pitch is below the critical flip depth of cut of the straight helix cutter multiplied by $\pi$, the flip lobes will totally vanish. This rule is not only valuable for chatter-free process planning purposes, but it also establishes exact limit below which the fast and simple zeroth order stability algorithm can provide exact stability boundaries for helical tools. The effectiveness of the formula is numerically corroborated over three different milling scenarios: thin wall milling, slender tool and machine tool structure chatter cases. Finally, the findings are validated through experimental cutting tests.

Laser powder bed fusion (LPBF) technology enables the development of NiTi alloys with complex geometries and tunable phase-transformation temperatures (PTTs). This technology is increasingly acknowledged as promising in the field of elastocaloric (eC) refrigeration. However, the mechanisms governing the manner in which this technology tunes the eC performance remain ambiguous. This study evaluated the fine-tuning of the eC properties by regulating Ni evaporation through laser manipulation. Our results demonstrate that although adjusting Ni loss via laser heat input can effectively control the PTTs, inappropriate combinations of laser parameters may result in lower than anticipated cooling capacity (ΔT_ad) and coefficient of performance (COP_mat) of produced samples. An excessive heat input results in Ni evaporation and in grain coarsening through the remelting and combination of fine grains owing to overlapping molten pools. Lower Ni enhances the phase-transformation enthalpy (ΔH_tr). However, larger grains increase the energy dissipation and thereby, counteracting ΔT_ad improvements. Theoretical analysis and experiments revealed that finer grains increase the misorientation angles. This hinders the dislocation motion and thereby, enhances the mechanical properties. Meanwhile, coarser grains can more conveniently promote PT and thereby, increase ΔH_tr. Thus, based on the naturally controllable grain size heterogeneity in LPBF-manufactured NiTi alloys, we propose optimizing the eC properties by controlling the morphology of the molten pool. Thermal-history simulations could balance this relationship. Ultimately, we developed two NiTi alloys for both high-temperature (70 °C) and room-temperature (25 °C) refrigeration. This study has provided effective insights for customizing high-performance eC components such as multistage caloric cascade regenerators, using additive manufacturing.

Despite the remarkable achievements in single-energy field-assisted diamond cutting technology, its performance remains unsatisfactory for processing high-entropy alloys (HEAs), targeted for next-generation large-scale industrial applications due to their exceptional properties. The challenge lies in overcoming the limitations of current single-energy field-assisted processing to achieve ultra-precision manufacturing of these advanced materials. This study proposes a multi-energy field-assisted ultra-precision machining technology, the magnetic and ultrasonic vibration dual-field assisted diamond cutting (MUVFDC), to address the current challenges. The phenomenological aspects of the dual-field coupling effect on HEAs are explored and investigated through comprehensive characterization of the workpiece material, ranging from macroscopic surface morphology to microscopic structural features. These analyses are performed based on experimental results from four different processing technologies: non-energy field, magnetic field, ultrasonic vibration field, and dual-field assisted machining. Research results demonstrate that MUVFDC technology effectively combines the advantages of a vibration field, which enhances cutting stability, and a magnetic field, which improves the machinability of materials. Additionally, this coupling technology addresses the challenges associated with single-energy field machining: it mitigates the difficulty of controlling surface scratches caused by tiny hard particles in a vibration field and suppresses the rapid tool wear encountered in a magnetic field. Furthermore, the gradient evolution of the subsurface microstructure reveals that the vibration field suppresses the severe matrix deformation induced by magnetic excitation. Simultaneously, the magnetic field reduces the size inhomogeneity of recrystallized grains caused by intermittent cutting. Overall, MUVFDC technology enhances surface quality, suppresses tool wear, smooths chip morphology, and reduces subsurface damage compared to single-energy field or non-energy-assisted machining. This work breaks through the performance limitations of traditional single-energy field-assisted processing and advances the understanding of the dual-field coupling effects in HEAs machining. It also presents a promising processing technology for the future ultra-precision manufacturing of advanced materials.

Bobbin-tool friction stir welding is a variant of friction stir welding with high process flexibility that has garnered considerable attention from the community. The reliability of the weld is sensitive to the macrostructure and texture of the stir zone, which must be carefully tailored. The macrostructure of the stir zone is governed by the refill behaviour of the plasticised metal associated with the bobbin-tool; refill occurs preferentially near the upper and lower shoulders, creating a triangular gap at the mid-thickness level that is subsequently closed by the confluence of the layered refilling plasticised metal from the upper and lower levels. Volumetric defects easily develop in this triangular confluence region because the symmetrical confluence of the layered refilling metal has the inherent characteristic of limited intermixing. The visual appearance of the triangular region, featuring limited voiding, was improved by tapering the stirring probe. This modification reduced the volume of displaced metal, leaving a smaller gap to be refilled during welding. Concurrently, the symmetrical confluence pattern was altered to an asymmetrical pattern, which enhanced the intermixing of the layered refilling metal from the upper and lower levels and promoted gap closure. For defect-free welds, macroscopic deformation inhomogeneity under tensile loading was observed due to the presence of a strong basal texture in the stir zone. The texture was scattered by disrupting the regular shear deformation pattern in the stir zone, which was achieved by modifying the tool profile. The activation capability of both basal slip and extension twinning among various local regions across the stir zone was substantially reduced through texture tailoring, resulting in more homogeneous tensile deformation. Consequently, elongation was enhanced by 66 %. This study highlights an easy-to-perform and generic strategy that can improve the quality of bobbin-tool friction stir welds.

Voronoi-based architected metamaterials have gained significant recognition as promising candidates for bone defect repair implants. However, the demanding requirements for reliable and adjustable load-bearing capacity pose challenges in applying irregular Voronoi-based architected metamaterials in implant applications. In this study, we propose a lattice-inspired design methodology for these metamaterials, enabling precise control over topologies and porosities to enhance their mechanical properties. We demonstrate the influence of unit cell topology on the printability, mechanical properties, and permeability of lattice-inspired Voronoi-based metamaterials (LIVMs) fabricated via laser powder bed fusion (LPBF) additive manufacturing. The LPBF-printed LIVMs exhibited yield strengths ranging from 3.35 to 17.59 MPa and specific energy absorption ranging from 3.81 to 14.29 J/g. Through finite element modeling and experimentation, we show that the deformation behavior of LIVMs with various topologies plays a crucial role in enhancing mechanical performance through mechanisms such as homogeneous load transfer between unit cells and multistage-contact strengthening within a unit cell. Additionally, we analyze the impact of unit cell type and porosity on the mass-transport behavior of LIVMs using computational fluid dynamics simulations. The LIVMs achieved experimental permeability values ranging from 3.88 × 10⁻⁹ to 16.83 × 10⁻⁹ m² (consistent with trabecular bones), indicating that multiple fluid flow channels can be utilized to enhance mass transport by distributing flow pressure and increasing fluid mobility. The proposed design method effectively achieves a favorable combination of superior mechanical properties and tunable permeability in Voronoi-based architected metamaterials. These findings provide valuable theoretical guidance for the development of architected metamaterials for bone implant applications.

The complexity of the interaction between the workpiece and abrasives, the characterisation difficulty of the strain-rate effect, and the analytical difficulty of brittle-ductile coexistence removal pose significant challenges in surface micro-morphology modelling of brittle-solid grinding. To overcome these bottlenecks, a theoretical model of the normal scratching force driven by the strain-rate effect was developed to verify the strain-rate sensitivity coefficients of gallium nitride (GaN) crystals. Impact scratching tests with a single grit further emphasised that the brittle-to-ductile transition and subsurface damage behaviour of GaN crystals exhibited a distinct strain-rate dependence. Subsequently, a theoretical model of the surface micro-morphology involved in the grinding of GaN crystals was developed by comprehensively considering the strain rate, abrasive coupling effect, time evolution, abrasive randomness, and elastic-to-plastic and brittle-to-ductile transition depths. The simulated results of the model agreed well with the experimental results, with an average error of <10 %. The model indicated that the ground surface micro-morphology and roughness were insensitive to variations in the grinding depth. Under the allowable conditions of the grinder stiffness and dynamic balance, appropriately increasing the wheel speed and grinding depth, decreasing the feed speed, and refining the abrasive size could effectively improve the proportion of ductile removal during the grinding of brittle solids. The results not only enhance the understanding of the abrasive coupling effect on surface micro-morphological evolution, material removal, and damage accumulation, but also provide theoretical guidance for the parameter optimisation involved in the grinding of brittle solids.

Laser shock peening, an advanced technology for severe surface plasticity peening, encounters challenges such as shallow hardened layers and surface spalling when dealing with difficult-to-machine materials. In this study, we introduced a high-frequency electropulsing-assisted laser shock peening (HFEP-LSP) technique that coupled laser shock peening with high-frequency electric pulses to achieve a significant and deeper plastic deformation layer. In the HFEP-LSP technique, we first considered the dual “skin effect”, which coupled the skin effect of high-frequency electric pulses with the “skin effect” of the mechanical effect induced by the laser shock wave. An integrated experimental platform comprising an electric pulse generator, laser shock peening equipment, and a control system was built. A >1.6 mm deep compressive residual stress layer was obtained, and the depth of the plastic deformation layer increased by 83.3 %. Furthermore, we elucidated the dual “skin effect”-induced complex heterostructure and β_m phase transition. A comprehensive analysis revealed the factors contributing to the deeper strengthening layer induced by HFEP-LSP, including the compressive residual stress and plastic deformation layers. In addition, the effects of laser shock peening and HFEP-LSP on the mechanical properties were investigated. Compared to the annealed samples, the ultimate tensile strength and elongation of the HFEP-LSP-treated samples were increased by 12.3 % and 57.1 %, respectively, with a fatigue life improvement of 176.4 %. The mechanism of synergistic improvement in strength and ductility was demonstrated.