Procedia CIRP最新文献

In modern manufacturing, machining remains a vital process for complex mechanical components. In particular, the aerospace industry extensively employs high-feed milling techniques to machine complex geometries from nickel-based superalloys. This study focuses on the analysis and modeling of high-feed milling for Inconel 718 in 2.5-axis machining. Its objective is to develop a generalized model of high-feed milling that enables the prediction of surface topography. The proposed model integrates crucial geometric parameters of the tool and its exact kinematic within the machine, along with tool and machine deflections caused by cutting forces. A key novelty of this research lies in its capability to determine surface topography and its quality based on a generalized model, representing significant progress in the field of high-feed milling. To validate the model, experimental efforts are measured to characterize the cutting forces and system deflections during machining. The developed approach demonstrates its ability to model surface topography and to predict surface roughness. It also highlights the influence of tool and machine deflection on surface quality. This research contributes to the advancement of the application of high-feed milling in aerospace manufacturing by enhancing machining capabilities and improving part quality.

High performance powder-based Ni-based superalloys exhibit exceptional in-service properties at elevated temperature, however this leads to reduced machinability and the potential for significant machining induced damage. Field assisted sintering technology (FAST) is capable of consolidating powder rapidly and efficiently, allowing for precise control of the microstructure via the dissolution of strengthening phases. In this study, subsolvus and supersolvus dwell temperatures were utilised to produce fine and coarse grain forms of an advanced Ni-based disk alloy. Surface integrity and machining forces were then evaluated after single point turning for a range of surface speeds. Higher cutting forces and lower depths of subsurface damage were generated when machining the fine grain (subsolvus) material when compared to the coarser grained (supersolvus) material. For both material conditions tested, higher surface speeds led to a reduced depth of subsurface deformation due to increased local temperatures, promoting workpiece softening. In addition, at higher cutting speeds the deformation of near surface γ’ precipitates were observed to be greater. These results demonstrate that the FAST process can be utilised to control microstructure, and as a result, tailor the machinability of Ni-based superalloy material.

SiC particles reinforced aluminum matrix (SiCp/Al) composites exhibit considerable potential for application in the aerospace and automobile manufacturing industries due to the characteristics of low density, high specific strength and high specific stiffness. However, machining of the composite material presents significant challenges owing to the presence of reinforced particles that result in complex friction at the tool-chip interface. This study presents the application of electric heat machining of 40 vol% SiCp/Al composites. A machining platform, equipped with a visual camera and an infrared imager, is employed to investigate the chip geometry, cutting forces, and cutting temperatures during the machining process. The findings indicate that electric heat machining offers the advantage of stabilizing cutting forces, with a corresponding reduction in cutting forces as electric power increase. Within a specific power range, a transition in chip geometry is observed, shifting from serrated to continuous, coinciding with a substantial decrease in cutting forces and a notable temperature rise within the shear zone. Furthermore, the results underscore the significant potential of electric heat machining for reducing cutting forces in the processing of SiCp/Al composites.

Quality analysis of additively manufactured (AM) surfaces is complex, yet critical for determining the functionality of parts and technology improvement. To accurately assess the quality of AM parts, it is necessary to consider the industrial application of the technology. This study investigates the variation of accumulated particles on AM top surfaces as a function of build position. It also seeks to study the surface texture variation as a function of build position, focusing on a spatial bandwidth region larger than that of traditional AM surface features, such as weld tracks, to investigate surface tension effects. Ti-6Al-4V cubes were built in a three-by-three array in a single build with fixed processing parameters. Coherence scanning interferometry was used to capture the primary data of the as-built top surfaces of cubes. The ISO 25178-2 methodology was used to extract the S-L surfaces, using the filtration methods defined in ISO 16610-21. The number of particles, coverage, and density were obtained by averaging over five repeated measurements in five different areas on the top surfaces. Particle distribution and surface texture analysis showed a trend from one location to another across the build, which is discussed according to the process variations.

This study investigates the influence of a cutting fluid during the drilling operation on the surface integrity and fatigue strength of 42CrMo4 hardened steel. The investigation includes characterizing surface topography, microstructure at different hole locations, and residual stresses. Fatigue tests were conducted, and the results were correlated with observations on surface integrity. The findings reveal that crack initiation occurs in a transition zone within the hole, where the cutting process evolves from pure cutting to a region with a strongly adhesive layer. The absence of cutting fluid leads to increased surface roughness and tensile residual stresses, resulting in a 28% reduction in fatigue strength.

This study aims to assess the effect of grinding on the surface integrity of rail materials. Two grinding processes (preventive and corrective) were employed along with the corresponding usage scenarios throughout a series of tests. For the purposes of testing, samples in the form of discs were utilised to assess the surface integrity of rails. Testing initially involved introducing some wear on the discs followed by the appropriate grinding process and then further testing to monitor the disc’s performance. More specifically the preventive grinding was utilised in a scenario where rail discs endured normal usage prior to grinding and corrective grinding process was employed in rails discs that had been run for extensive cycles (2.5 times longer compared to normal usage) to generate significant wear before grinding. After the maintenance process all the specimens were further examined to assess their post-grinding performance. The experiments revealed that the aggressive single grinding pass methodology followed in a corrective maintenance approach could lead to undesirable results as the increased heat input, high surface roughness as well as the initial cracks from the prolonged pre-grinding running period could have an adverse effect on the RCF life. This was demonstrated by an almost triple wear rate compared to the “normal” usage scenario during the post-grinding testing.

Powder mixed electrical discharge machining (PMEDM) with silver nano-powder has demonstrated its potential capability in antibacterial surface modification. Analyses in the cross-sectional layer showed that silver was mainly integrated near the topmost surface layer, and its content is reduced within the layer towards the substrate. However, to achieve a long-term antibacterial efficacy, silver needs to be deeply integrated in the modified layer.

Previous studies indicated that ultrasonic vibration (UV) assisted PMEDM can homogenize the silver content in the deposited layer. In this study, the effect of UV on the silver distribution within the modified layer is investigated. Ti6Al4V workpieces were stimulated by UV with a frequency of 22.3 kHz and an amplitude of 2.5 µm. Hydrocarbon-based dielectric fluid, mixed with silver nano-powder with concentrations up to 15 g/L, were internally flushed through a hollow tool with a pressure of 4 bar. PMEDM without UV was investigated for comparison. The layer thickness, micro-cracks and the cross-sectional distribution of deposited silver were analysed by confocal microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Results indicate that applying UV leads to the highest silver content in the middle region of the layer, a significant decrease of micro-cracks and a slight reduction of the layer thickness.

In most powder bed-based laser melting systems (PBF-LB), metal powders must be handled without inertization but in an air atmosphere for a short time, increasing the AlSi10Mg powder moisture and reducing the achievable component density. Consequently, different drying methods were investigated. Drying in a furnace with an inert atmosphere, using a vacuum to evaporate the water at low temperatures, and vaporizing moisture layerwise from the spreaded powder with a defocused, low-power laser beam as a further process step of the PBF-LB process. Therefore, four different moisturized powders, which were dried with different settings for the drying methods, are analyzed. All drying methods reduce the moisture content of the powder, with in-process drying being the most effective. Due to the oxide layer growth around the particles during furnace and vacuum drying, the achievable sample density after drying is worse. In-process drying with low energy density is the best option to reach a reduction of hydrogen pores and an increase of density.

Tool inserts for injection moulding must serve various requirements being contradictive to each other. The best approach to enhance the functionality of a tool insert, i.e., providing good wear and corrosion resistance as well as good toughness, is to employ a multi-material approach. This study investigates a concept for manufacture of a material-tailored multi-material tool insert using Material Extrusion additive manufacturing of metals (MEX/M). The processing of AISI A2 (1.2363) and AISI 420 (1.2083) steel as a wear-resistant and corrosion-resistant material, respectively, in combination with AISI H11 (1.2343) as a tough bulk material were investigated. The eligibility of these materials for co-sintering was evaluated based on shrinkage and resulting density after sintering. A material-tailored tool insert was manufactured by means of MEX/M demonstrating its capability for multi-material additive manufacturing. Elemental distribution at the interface was analysed. Surface quality of the multi-material tool insert was evaluated taking into account extruder trajectories.

This study extends an existing comprehensive computational framework to gain insight on hot cracking in the simulation of laser-based additive manufacturing via powder bed fusion. A novel approach to predict hot crack susceptibility based on vapor cavitation, building on a conceptual model akin to the Rappaz-Drezet-Gremaud criterion is introduced. Unlike conventional practices involving ex-situ evaluation of a criterion, the proposed model emerges implicitly from the underlying multiphysical modeling framework. The model exhibits sensitivity to variations in both material attributes (e.g., alloy composition) and processing conditions (e.g., laser beam shape or scanning strategy). Furthermore, non-equilibrium solidification is incorporated in the underlying Mass-of-Fluid framework, and a model for multi-layer printing is introduced to extend the length and time scale, enabling the derivation of detailed thermal histories on near-part-scale level. Consequently, the framework proves pivotal in optimizing process parameters, transcending the limitations inherent in conventional single melt track computational experiments.