Procedia CIRP最新文献

The in-process detection of grinding burns has earned considerable interest from both researchers and industries in recent years. Various Non-destructive testing (NDT) technologies, including Eddy Current (EC), Barkhausen Noise (BN), and Acoustic Emission sensors (AE), have been employed to address this issue, yielding successful results for specific applications. However, a comprehensive understanding of burn generation and its prevention in grinding operations remains an area of interest that has not yet been fully resolved.

This paper focuses on investigating the electromagnetic response of a custom-made EC sensor applied to UNE F-522 (AISI 01) steel during in-process inspections. Experimental grinding tests have been performed using a special EC inspection head installed in the grinding machine. The impedance change of the material during grinding is discussed in terms of the machine out-puts (Power consumption) and other grinding variables, such as number of passes, the roughing stock removal, and the finishing strategy. The experimental results demonstrate that the proposed EC technology not only enables the detection of burns, but also enhances comprehension of the surface integrity changes occurring during the grinding process.

Powder metallurgy (PM) processed nickel-based superalloys are increasingly employed in the hot section of gas turbine engines for parts such as high-pressure (HP) compressors and turbine rotor discs over more traditional cast and wrought options such as Inconel 718 due to its improved high-temperature properties. In this paper, the surface integrity and geometrical/dimensional accuracy of holes initially rough drilled using worn tools and subsequently finish plunge end milled in a proprietary PM-processed Ni-based superalloy, were assessed and compared. The influence of tool wear on hole quality after finish plunge end milling was also investigated. Significant improvement in hole quality was evident following finishing with reductions in surface roughness (up to ~86%), subsurface microhardness (up to ~125 HK_0.05) and workpiece microstructure deformation/damage (up to ~80% in terms of average depth) compared to corresponding rough drilled holes. Evidence of chatter marks on holes machined with worn plunge end mills was observed, despite exhibiting reduced surface roughness levels (~45-73%). Generally, somewhat improved hole surface integrity (reduced subsurface deformation by ~47-64%) and geometrical accuracy (circularity decreased by ~10-25%) were produced when employing new tools.

In the large-aperture lens manufacturing, not only high surface quality but also high productivity is required. From this perspective, Reaction-Induced-Slurry-Assisted grinding (RISA grinding), in which cerium oxide slurry is supplied instead of using general grinding fluid, has been developed to achieve high surface quality at high removal rate. However, the surface profile error becomes large due to chemical removal effect of the cerium oxide slurry. Therefore, the purpose of this study is to experimentally investigate the influence of the chemical removal effect on the surface profile error using AE signals and servo current signals in RISA grinding. First, relation between dwell time and removal depth is analyzed by conducting a basic grinding test without the workpiece rotation. The result shows that the actual removal depth increases with increase of dwell time despite applying the constant depth of cut. Then, zero-cut RISA grinding test is conducted. It is found that the removal process proceeds even though zero-cut grinding, and its removal rate varies according to the wheel feed rate. Furthermore, the amount of cerium oxide abrasives adhered to the grinding wheel can be estimated from the AE signals and servo current signals.

The utilization of lattice structure in engineering components by additive manufacturing (AM) is gaining attention due to its lightweight design, high strength-to-weight ratio, and effective material utilization. Producing holes in additively manufactured lattice structures with dimensional accuracy is challenging. In the current study, we fabricate near circular through-holes on deterministic lattice structured components fabricated by laser powder bed fusion by utilizing electric discharge machining (EDM). In the additively manufactured Inconel 718 (IN718) lattice structure, nodes are connected by strut leaving voids/pores amongst different nodal points. Due to EDM, the nodes at the boundary of the hole experience concentration plasma interaction, heating, and rapid cooling, which causes a substantial change in the microstructure. The selective removal of material from different nodal positions causes uncharacteristic recast layers, partial damages, and uncontrolled cracking of the struts. In the present study, we investigated and characterized the differential behaviour and mechanism of various surface integrity issues associated with the selective material removal of LPBF IN718 lattice structures and their elements (nodes and struts).

The paper deals with a novel method for the edge preparation of cutting tools using an advanced approach. Cemented carbide cutting inserts were used as a sample in the experiment, and were prepared using plasma discharges in electrolyte. This technique is an environmentally-friendlier method in contrast to electropolishing treatment. The experiment aimed to determine the influence of process parameters of plasma treatment on the material removal rate and cutting edge radius size. In the experiment, concentration of electrolyte, voltage between electrodes, temperature of electrolyte, and operating time were varied. The material removal rate and cutting edge radius size increased faster with the decreasing concentration of electrolyte, decreasing voltage, and decreasing temperature of electrolyte. The material removal percentage increase was 155 percent, and 57 percent for cutting edge radius size during the 10 seconds of operation time in the specified range of process parameters. This change can be achieved by setting various process parameters. The results of the experiment proved that plasma treatment can control the forming of cutting edge radii. Cutting edge preparation using plasma discharges in electrolyte takes only a few seconds, depending on the cutting edge radius sizes.

This research investigates the surface properties of 316L stainless steel machined by combining two wire electro manufacturing processes on a single machining platform, i.e., wire EDM roughing and wire ECM finishing. While the former is well known in industry, the latter has not yet seen much industrial use but can improve the surface integrity since it does not generate heat to achieve material removal, avoiding several EDM (semi)finishing passes at reduced sparking energies. With applications in the medical, energy, and aerospace fields, this research focuses on characterizing the machined surfaces with respect to the surface defects and the chemical composition. The studied surface properties include the (sub)surface morphology with respect to micro cracks and heat related damage introduced by wire EDM, and the mechanism of their removal by wire ECM finishing. The chemical composition of the surface is furthermore evaluated to characterize the contamination of the workpiece material by the tool electrode material. The manufactured samples are studied using a profilometer to quantify material removal and the resulting roughness. Metallographic analysis is carried out by optical microscopy and SEM with EDX. Initial results show an average surface roughness below 0.1 µm Ra by applying a wire ECM finishing pass after wire EDM.

Machining-induced residual stress significantly impacts the fatigue life and service performance of machined components. Appropriate compressive residual stress can enhance resistance to crack initiation, while tensile residual stress may be detrimental. In this study, an inverse analysis is conducted to optimize the cutting parameters for achieving desired residual stresses. The analysis begins by predicting the machining-induced thermal-mechanical loads in the primary shear zones using analytical methods. Subsequently, an Arbitrary Lagrangian-Eulerian (ALE) based numerical model is proposed to calculate the resulting residual stresses by incorporating the determined thermal-mechanical loads. This analytical-numerical hybrid method facilitates rapid and accurate modeling of residual stresses. Then, the Newton’s method is employed to deduce cutting parameters iteratively, ensuring a proper residual stress. Finally, the results of inverse analysis are compared with experimental measurements to validate its efficacy.

Several 10 ℓ/min of cooling lubricants are used to cool and lubricate the cutting edges during conventional mechanical milling of lightweight metals. Different concepts of minimum quantity lubrication (between 5 mℓ/h and 50 mℓ/h) have been developed in the past since the recycling and disposal of the cooling lubricants is energy-intensive and costly. One promising approach for minimum quantity lubrication during milling processes with closed cutting edges is the passive directional transport of the lubricant along the chip guiding surfaces to the milling area.

Laser micromachining with ultrashort laser pulses was used for the fabrication of bionic transport structures on tools made from cemented tungsten carbide. An analytical model for the prediction of the dimensions of the transport structures was derived and experimentally verified. The microscopic surface structures that form on the surface of the transport structures were investigated and their wetting behavior for different lubricants and deionized water was characterized by contact angle measurements. A low contact angle <6° was achieved with laser wavelength-sized ripples on the surface. Finally, passive directional transport of lubricants on tools made from cemented tungsten carbide could be demonstrated with bionic transport structures over a distance of up to 60 mm.

In this article, the potential of high-speed machining with an inverse cutting ratio b/h < 1 (uncut width of chip b to uncut chip thickness h) is presented based on the evaluation of surface integrity. If the machining is realized with a low cutting ratio many process quantities and chip formation mechanisms are fundamentally changed. As a result, the cutting process is stabilized through reduced feed forces and improved chip removal conditions. For the investigations, face-milling trials were carried out on an aluminum alloy (EN AC-42100) under conventional and high cutting speeds with variation of the feed per tooth and the use of cemented carbide and polycrystalline diamond tools. It is shown that when both machining strategies are combined, there is no further reduction in force components or improvement in surface topography. When the feed per tooth is increased at high cutting speeds, there is a linear increase in force components but surface roughness remain almost unchanged. After an initial increase in surface residual stresses, increasing the cutting speed leads mainly to compressive surface residual stresses. Overall, the surface integrity is influenced by the choice of cutting material and the micro-geometry of the cutting edge radius.

Vibration-assisted cutting is a promising technique widely utilized to enhance machining efficiency and achieve superior material finishes compared to traditional cutting methods. However, the underlying mechanism of how vibration impacts material properties and deformation requires an in-depth understanding. In this study, molecular dynamics (MD) simulations were employed to investigate the atomic-scale effects of vibration on copper. The result reveals significant changes in the mechanical behaviours of copper under different cutting conditions. The high-frequency vibration of the cutting tool introduces a notable temperature rise to the workpiece, which is considered beneficial for improving the material removal efficiency. Additionally, the cyclic loading of the tool assists in reducing cutting forces and polishing the machined surface to enhance the surface integrity. Furthermore, the analysis of dislocations and defects suggests that vibration effectively prevents large-scale lattice deformations and visible cracks, thereby enhancing surface finish. This research provides insights into the role of vibration in improving cutting processes and surface quality.